diff --git a/core/fxcrt/BUILD.gn b/core/fxcrt/BUILD.gn
index d4a986d..b582acc 100644
--- a/core/fxcrt/BUILD.gn
+++ b/core/fxcrt/BUILD.gn
@@ -62,6 +62,7 @@
     "string_data_template.h",
     "string_pool_template.h",
     "string_view_template.h",
+    "timerhandler_iface.h",
     "tree_node.h",
     "unowned_ptr.h",
     "weak_ptr.h",
diff --git a/core/fxcrt/timerhandler_iface.h b/core/fxcrt/timerhandler_iface.h
new file mode 100644
index 0000000..05f241e
--- /dev/null
+++ b/core/fxcrt/timerhandler_iface.h
@@ -0,0 +1,29 @@
+// Copyright 2019 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#ifndef CORE_FXCRT_TIMERHANDLER_IFACE_H_
+#define CORE_FXCRT_TIMERHANDLER_IFACE_H_
+
+#include "core/fxcrt/fx_system.h"
+
+namespace fxcrt {
+
+class TimerHandlerIface {
+ public:
+  static constexpr int32_t kInvalidTimerID = 0;
+  using TimerCallback = void (*)(int32_t idEvent);
+
+  virtual ~TimerHandlerIface() = default;
+
+  virtual int32_t SetTimer(int32_t uElapse, TimerCallback lpTimerFunc) = 0;
+  virtual void KillTimer(int32_t nID) = 0;
+};
+
+}  // namespace fxcrt
+
+using fxcrt::TimerHandlerIface;
+
+#endif  // CORE_FXCRT_TIMERHANDLER_IFACE_H_
diff --git a/fpdfsdk/cfx_systemhandler.h b/fpdfsdk/cfx_systemhandler.h
index 49297cd..733cce9 100644
--- a/fpdfsdk/cfx_systemhandler.h
+++ b/fpdfsdk/cfx_systemhandler.h
@@ -8,30 +8,27 @@
 #define FPDFSDK_CFX_SYSTEMHANDLER_H_
 
 #include "core/fxcrt/fx_coordinates.h"
-#include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
 #include "core/fxcrt/unowned_ptr.h"
+#include "fpdfsdk/pwl/ipwl_systemhandler.h"
 
 class CFFL_FormFiller;
-class CPDF_Document;
 class CPDFSDK_FormFillEnvironment;
 class CPDFSDK_Widget;
 
-class CFX_SystemHandler {
+class CFX_SystemHandler final : public IPWL_SystemHandler {
  public:
-  static constexpr int32_t kInvalidTimerID = 0;
-  using TimerCallback = void (*)(int32_t idEvent);
-
   explicit CFX_SystemHandler(CPDFSDK_FormFillEnvironment* pFormFillEnv);
-  ~CFX_SystemHandler();
+  ~CFX_SystemHandler() override;
 
-  void InvalidateRect(CPDFSDK_Widget* widget, const CFX_FloatRect& rect);
+  void InvalidateRect(CPDFSDK_Widget* widget,
+                      const CFX_FloatRect& rect) override;
   void OutputSelectedRect(CFFL_FormFiller* pFormFiller,
-                          const CFX_FloatRect& rect);
-  bool IsSelectionImplemented() const;
-  void SetCursor(int32_t nCursorType);
-  int32_t SetTimer(int32_t uElapse, TimerCallback lpTimerFunc);
-  void KillTimer(int32_t nID);
+                          const CFX_FloatRect& rect) override;
+  bool IsSelectionImplemented() const override;
+  void SetCursor(int32_t nCursorType) override;
+  int32_t SetTimer(int32_t uElapse, TimerCallback lpTimerFunc) override;
+  void KillTimer(int32_t nID) override;
 
  private:
   UnownedPtr<CPDFSDK_FormFillEnvironment> const m_pFormFillEnv;
diff --git a/fpdfsdk/formfiller/cffl_formfiller.cpp b/fpdfsdk/formfiller/cffl_formfiller.cpp
index 11074f9..1040172 100644
--- a/fpdfsdk/formfiller/cffl_formfiller.cpp
+++ b/fpdfsdk/formfiller/cffl_formfiller.cpp
@@ -580,7 +580,7 @@
 
 void CFFL_FormFiller::TimerProc() {}
 
-CFX_SystemHandler* CFFL_FormFiller::GetSystemHandler() const {
+IPWL_SystemHandler* CFFL_FormFiller::GetSystemHandler() const {
   return m_pFormFillEnv->GetSysHandler();
 }
 
diff --git a/fpdfsdk/formfiller/cffl_formfiller.h b/fpdfsdk/formfiller/cffl_formfiller.h
index 0f098e2..0397c1f 100644
--- a/fpdfsdk/formfiller/cffl_formfiller.h
+++ b/fpdfsdk/formfiller/cffl_formfiller.h
@@ -83,9 +83,9 @@
   void SetFocusForAnnot(CPDFSDK_Annot* pAnnot, uint32_t nFlag);
   void KillFocusForAnnot(uint32_t nFlag);
 
-  // CPWL_TimerHandler
+  // CPWL_TimerHandler:
   void TimerProc() override;
-  CFX_SystemHandler* GetSystemHandler() const override;
+  IPWL_SystemHandler* GetSystemHandler() const override;
 
   // CPWL_Wnd::ProviderIface:
   CFX_Matrix GetWindowMatrix(const CPWL_Wnd::PrivateData* pAttached) override;
diff --git a/fpdfsdk/pwl/BUILD.gn b/fpdfsdk/pwl/BUILD.gn
index a771aa5..b018d53 100644
--- a/fpdfsdk/pwl/BUILD.gn
+++ b/fpdfsdk/pwl/BUILD.gn
@@ -36,6 +36,7 @@
     "cpwl_timer_handler.h",
     "cpwl_wnd.cpp",
     "cpwl_wnd.h",
+    "ipwl_systemhandler.h",
   ]
   configs += [ "../../:pdfium_core_config" ]
   deps = [
diff --git a/fpdfsdk/pwl/cpwl_edit.cpp b/fpdfsdk/pwl/cpwl_edit.cpp
index 1aab8ef..6ce6a0f 100644
--- a/fpdfsdk/pwl/cpwl_edit.cpp
+++ b/fpdfsdk/pwl/cpwl_edit.cpp
@@ -237,7 +237,7 @@
     pRange = &wrRange;
   }
 
-  CFX_SystemHandler* pSysHandler = GetSystemHandler();
+  IPWL_SystemHandler* pSysHandler = GetSystemHandler();
   CPWL_EditImpl::DrawEdit(pDevice, mtUser2Device, m_pEdit.get(),
                           GetTextColor().ToFXColor(GetTransparency()), rcClip,
                           CFX_PointF(), pRange, pSysHandler,
@@ -279,7 +279,7 @@
   if (!HasFlag(PES_TEXTOVERFLOW) && !ClientHitTest(point))
     return true;
 
-  CFX_SystemHandler* pSH = GetSystemHandler();
+  IPWL_SystemHandler* pSH = GetSystemHandler();
   if (!pSH)
     return false;
 
diff --git a/fpdfsdk/pwl/cpwl_edit_ctrl.cpp b/fpdfsdk/pwl/cpwl_edit_ctrl.cpp
index 7e03e55..9b874c1 100644
--- a/fpdfsdk/pwl/cpwl_edit_ctrl.cpp
+++ b/fpdfsdk/pwl/cpwl_edit_ctrl.cpp
@@ -41,7 +41,7 @@
 
 void CPWL_EditCtrl::SetCursor() {
   if (IsValid()) {
-    if (CFX_SystemHandler* pSH = GetSystemHandler()) {
+    if (IPWL_SystemHandler* pSH = GetSystemHandler()) {
       if (IsWndHorV())
         pSH->SetCursor(FXCT_VBEAM);
       else
diff --git a/fpdfsdk/pwl/cpwl_edit_impl.cpp b/fpdfsdk/pwl/cpwl_edit_impl.cpp
index 80e1367..6197dd7 100644
--- a/fpdfsdk/pwl/cpwl_edit_impl.cpp
+++ b/fpdfsdk/pwl/cpwl_edit_impl.cpp
@@ -21,10 +21,10 @@
 #include "core/fxge/cfx_graphstatedata.h"
 #include "core/fxge/cfx_pathdata.h"
 #include "core/fxge/cfx_renderdevice.h"
-#include "fpdfsdk/cfx_systemhandler.h"
 #include "fpdfsdk/pwl/cpwl_edit.h"
 #include "fpdfsdk/pwl/cpwl_edit_ctrl.h"
 #include "fpdfsdk/pwl/cpwl_scroll_bar.h"
+#include "fpdfsdk/pwl/ipwl_systemhandler.h"
 #include "third_party/base/compiler_specific.h"
 #include "third_party/base/ptr_util.h"
 
@@ -458,7 +458,7 @@
                              const CFX_FloatRect& rcClip,
                              const CFX_PointF& ptOffset,
                              const CPVT_WordRange* pRange,
-                             CFX_SystemHandler* pSystemHandler,
+                             IPWL_SystemHandler* pSystemHandler,
                              CFFL_FormFiller* pFFLData) {
   const bool bContinuous =
       pEdit->GetCharArray() == 0 && pEdit->GetCharSpace() <= 0.0f;
diff --git a/fpdfsdk/pwl/cpwl_edit_impl.h b/fpdfsdk/pwl/cpwl_edit_impl.h
index 889ed78..1e36b2e 100644
--- a/fpdfsdk/pwl/cpwl_edit_impl.h
+++ b/fpdfsdk/pwl/cpwl_edit_impl.h
@@ -25,9 +25,9 @@
 class CPWL_EditImpl_Iterator;
 class CPWL_EditImpl_Provider;
 class CFX_RenderDevice;
-class CFX_SystemHandler;
 class CPWL_Edit;
 class CPWL_EditCtrl;
+class IPWL_SystemHandler;
 class IFX_Edit_UndoItem;
 
 struct CPWL_EditImpl_LineRect {
@@ -261,7 +261,7 @@
                        const CFX_FloatRect& rcClip,
                        const CFX_PointF& ptOffset,
                        const CPVT_WordRange* pRange,
-                       CFX_SystemHandler* pSystemHandler,
+                       IPWL_SystemHandler* pSystemHandler,
                        CFFL_FormFiller* pFFLData);
 
   CPWL_EditImpl();
diff --git a/fpdfsdk/pwl/cpwl_list_box.cpp b/fpdfsdk/pwl/cpwl_list_box.cpp
index 6b9f837..b64b4a0 100644
--- a/fpdfsdk/pwl/cpwl_list_box.cpp
+++ b/fpdfsdk/pwl/cpwl_list_box.cpp
@@ -113,8 +113,8 @@
         rcItem.Intersect(rcClient);
     }
 
+    IPWL_SystemHandler* pSysHandler = GetSystemHandler();
     if (m_pList->IsItemSelected(i)) {
-      CFX_SystemHandler* pSysHandler = GetSystemHandler();
       if (pSysHandler && pSysHandler->IsSelectionImplemented()) {
         CPWL_EditImpl::DrawEdit(pDevice, mtUser2Device, m_pList->GetItemEdit(i),
                                 GetTextColor().ToFXColor(255), rcList, ptOffset,
@@ -129,7 +129,6 @@
                                 m_pFormFiller.Get());
       }
     } else {
-      CFX_SystemHandler* pSysHandler = GetSystemHandler();
       CPWL_EditImpl::DrawEdit(pDevice, mtUser2Device, m_pList->GetItemEdit(i),
                               GetTextColor().ToFXColor(255), rcList, ptOffset,
                               nullptr, pSysHandler, nullptr);
diff --git a/fpdfsdk/pwl/cpwl_timer.cpp b/fpdfsdk/pwl/cpwl_timer.cpp
index b5436d4..cb02b43 100644
--- a/fpdfsdk/pwl/cpwl_timer.cpp
+++ b/fpdfsdk/pwl/cpwl_timer.cpp
@@ -21,7 +21,7 @@
 }  // namespace
 
 CPWL_Timer::CPWL_Timer(CPWL_TimerHandler* pAttached,
-                       CFX_SystemHandler* pSystemHandler)
+                       IPWL_SystemHandler* pSystemHandler)
     : m_pAttached(pAttached), m_pSystemHandler(pSystemHandler) {
   ASSERT(m_pAttached);
   ASSERT(m_pSystemHandler);
@@ -46,7 +46,7 @@
 
   m_pSystemHandler->KillTimer(m_nTimerID);
   GetPWLTimeMap().erase(m_nTimerID);
-  m_nTimerID = CFX_SystemHandler::kInvalidTimerID;
+  m_nTimerID = IPWL_SystemHandler::kInvalidTimerID;
 }
 
 // static
diff --git a/fpdfsdk/pwl/cpwl_timer.h b/fpdfsdk/pwl/cpwl_timer.h
index 79259fe..a77cacb 100644
--- a/fpdfsdk/pwl/cpwl_timer.h
+++ b/fpdfsdk/pwl/cpwl_timer.h
@@ -8,13 +8,13 @@
 #define FPDFSDK_PWL_CPWL_TIMER_H_
 
 #include "core/fxcrt/unowned_ptr.h"
-#include "fpdfsdk/cfx_systemhandler.h"
+#include "fpdfsdk/pwl/ipwl_systemhandler.h"
 
 class CPWL_TimerHandler;
 
 class CPWL_Timer {
  public:
-  CPWL_Timer(CPWL_TimerHandler* pAttached, CFX_SystemHandler* pSystemHandler);
+  CPWL_Timer(CPWL_TimerHandler* pAttached, IPWL_SystemHandler* pSystemHandler);
   ~CPWL_Timer();
 
   static void TimerProc(int32_t idEvent);
@@ -24,12 +24,12 @@
 
  private:
   bool HasValidID() const {
-    return m_nTimerID != CFX_SystemHandler::kInvalidTimerID;
+    return m_nTimerID != IPWL_SystemHandler::kInvalidTimerID;
   }
 
-  int32_t m_nTimerID = CFX_SystemHandler::kInvalidTimerID;
+  int32_t m_nTimerID = IPWL_SystemHandler::kInvalidTimerID;
   UnownedPtr<CPWL_TimerHandler> const m_pAttached;
-  UnownedPtr<CFX_SystemHandler> const m_pSystemHandler;
+  UnownedPtr<IPWL_SystemHandler> const m_pSystemHandler;
 };
 
 #endif  // FPDFSDK_PWL_CPWL_TIMER_H_
diff --git a/fpdfsdk/pwl/cpwl_timer_handler.h b/fpdfsdk/pwl/cpwl_timer_handler.h
index f208e1c..67c117e 100644
--- a/fpdfsdk/pwl/cpwl_timer_handler.h
+++ b/fpdfsdk/pwl/cpwl_timer_handler.h
@@ -9,8 +9,8 @@
 
 #include <memory>
 
-class CFX_SystemHandler;
 class CPWL_Timer;
+class IPWL_SystemHandler;
 
 class CPWL_TimerHandler {
  public:
@@ -18,7 +18,7 @@
   virtual ~CPWL_TimerHandler();
 
   virtual void TimerProc();
-  virtual CFX_SystemHandler* GetSystemHandler() const = 0;
+  virtual IPWL_SystemHandler* GetSystemHandler() const = 0;
 
   void BeginTimer(int32_t nElapse);
   void EndTimer();
diff --git a/fpdfsdk/pwl/cpwl_wnd.cpp b/fpdfsdk/pwl/cpwl_wnd.cpp
index 3d8e84d..6316ced 100644
--- a/fpdfsdk/pwl/cpwl_wnd.cpp
+++ b/fpdfsdk/pwl/cpwl_wnd.cpp
@@ -268,7 +268,7 @@
   rcWin.Inflate(1, 1);
   rcWin.Normalize();
 
-  CFX_SystemHandler* pSH = GetSystemHandler();
+  IPWL_SystemHandler* pSH = GetSystemHandler();
   if (!pSH)
     return true;
 
@@ -606,7 +606,7 @@
 
 void CPWL_Wnd::SetCursor() {
   if (IsValid()) {
-    if (CFX_SystemHandler* pSH = GetSystemHandler())
+    if (IPWL_SystemHandler* pSH = GetSystemHandler())
       pSH->SetCursor(GetCreationParams()->eCursorType);
   }
 }
@@ -662,7 +662,7 @@
   m_CreationParams.fFontSize = fFontSize;
 }
 
-CFX_SystemHandler* CPWL_Wnd::GetSystemHandler() const {
+IPWL_SystemHandler* CPWL_Wnd::GetSystemHandler() const {
   return m_CreationParams.pSystemHandler.Get();
 }
 
diff --git a/fpdfsdk/pwl/cpwl_wnd.h b/fpdfsdk/pwl/cpwl_wnd.h
index b0adc89..2349783 100644
--- a/fpdfsdk/pwl/cpwl_wnd.h
+++ b/fpdfsdk/pwl/cpwl_wnd.h
@@ -22,8 +22,8 @@
 class CPWL_Edit;
 class CPWL_MsgControl;
 class CPWL_ScrollBar;
-class CFX_SystemHandler;
 class IPVT_FontMap;
+class IPWL_SystemHandler;
 struct PWL_SCROLL_INFO;
 
 // window styles
@@ -121,7 +121,7 @@
     ~CreateParams();
 
     CFX_FloatRect rcRectWnd;                          // required
-    UnownedPtr<CFX_SystemHandler> pSystemHandler;     // required
+    UnownedPtr<IPWL_SystemHandler> pSystemHandler;    // required
     UnownedPtr<IPVT_FontMap> pFontMap;                // required
     ObservedPtr<ProviderIface> pProvider;             // required
     UnownedPtr<FocusHandlerIface> pFocusHandler;      // optional
@@ -262,7 +262,7 @@
 
  protected:
   // CPWL_TimerHandler:
-  CFX_SystemHandler* GetSystemHandler() const override;
+  IPWL_SystemHandler* GetSystemHandler() const override;
 
   virtual void CreateChildWnd(const CreateParams& cp);
 
diff --git a/fpdfsdk/pwl/ipwl_systemhandler.h b/fpdfsdk/pwl/ipwl_systemhandler.h
new file mode 100644
index 0000000..3607e73
--- /dev/null
+++ b/fpdfsdk/pwl/ipwl_systemhandler.h
@@ -0,0 +1,29 @@
+// Copyright 2019 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#ifndef FPDFSDK_PWL_IPWL_SYSTEMHANDLER_H_
+#define FPDFSDK_PWL_IPWL_SYSTEMHANDLER_H_
+
+#include "core/fxcrt/fx_coordinates.h"
+#include "core/fxcrt/fx_system.h"
+#include "core/fxcrt/timerhandler_iface.h"
+
+class CPDFSDK_Widget;
+class CFFL_FormFiller;
+
+class IPWL_SystemHandler : public TimerHandlerIface {
+ public:
+  ~IPWL_SystemHandler() override = default;
+
+  virtual void InvalidateRect(CPDFSDK_Widget* widget,
+                              const CFX_FloatRect& rect) = 0;
+  virtual void OutputSelectedRect(CFFL_FormFiller* pFormFiller,
+                                  const CFX_FloatRect& rect) = 0;
+  virtual bool IsSelectionImplemented() const = 0;
+  virtual void SetCursor(int32_t nCursorType) = 0;
+};
+
+#endif  // FPDFSDK_PWL_IPWL_SYSTEMHANDLER_H_
diff --git a/fxjs/global_timer.cpp b/fxjs/global_timer.cpp
index a4d3c04..88ea27b 100644
--- a/fxjs/global_timer.cpp
+++ b/fxjs/global_timer.cpp
@@ -8,7 +8,7 @@
 
 #include <map>
 
-#include "fpdfsdk/cfx_systemhandler.h"
+#include "core/fxcrt/timerhandler_iface.h"
 #include "fxjs/cjs_app.h"
 
 namespace {