Add CXFA_Document::GetHeap().

Since CXFA_Document creates the various CXFA_Nodes, this will be a big
help in allowing them to be GC'd down the road. The heap is reachable,
but is a couple of hops away, so add the function here rather than
making callers do these steps over and over.

-- Move some forward declarations even more forward.

Change-Id: Ic589bf7d4a4c47cc69344226ffd1c48def3585be
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/71390
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

xfa/fxfa/cxfa_ffdoc.h

diff --git a/xfa/fxfa/cxfa_ffdoc.h b/xfa/fxfa/cxfa_ffdoc.h
index 67852e4..461ffaa 100644
--- a/xfa/fxfa/cxfa_ffdoc.h
+++ b/xfa/fxfa/cxfa_ffdoc.h
@@ -58,6 +58,7 @@
     return m_pDocEnvironment.Get();
   }
   FormType GetFormType() const { return m_FormType; }
+  cppgc::Heap* GetHeap() const { return m_pHeap.Get(); }
   CFX_XMLDocument* GetXMLDocument() const { return m_pXMLDoc.get(); }
 
   CXFA_FFDocView* CreateDocView();

xfa/fxfa/parser/cxfa_document.cpp

diff --git a/xfa/fxfa/parser/cxfa_document.cpp b/xfa/fxfa/parser/cxfa_document.cpp
index b62d94c..98d65c0 100644
--- a/xfa/fxfa/parser/cxfa_document.cpp
+++ b/xfa/fxfa/parser/cxfa_document.cpp
@@ -1412,6 +1412,10 @@
   return m_pLocaleMgr.get();
 }
 
+cppgc::Heap* CXFA_Document::GetHeap() const {
+  return notify_->GetFFDoc()->GetHeap();
+}
+
 CFXJSE_Engine* CXFA_Document::InitScriptContext(CJS_Runtime* fxjs_runtime) {
   ASSERT(!m_pScriptContext);
   m_pScriptContext = std::make_unique<CFXJSE_Engine>(this, fxjs_runtime);

xfa/fxfa/parser/cxfa_document.h

diff --git a/xfa/fxfa/parser/cxfa_document.h b/xfa/fxfa/parser/cxfa_document.h
index 8509d19..c9fa4bf 100644
--- a/xfa/fxfa/parser/cxfa_document.h
+++ b/xfa/fxfa/parser/cxfa_document.h
@@ -17,6 +17,22 @@
 #include "xfa/fxfa/parser/cxfa_localemgr.h"
 #include "xfa/fxfa/parser/cxfa_nodeowner.h"
 
+class CFXJSE_Engine;
+class CJS_Runtime;
+class CScript_DataWindow;
+class CScript_EventPseudoModel;
+class CScript_HostPseudoModel;
+class CScript_LayoutPseudoModel;
+class CScript_LogPseudoModel;
+class CScript_SignaturePseudoModel;
+class CXFA_FFNotify;
+class CXFA_Node;
+class CXFA_Object;
+
+namespace cppgc {
+class Heap;
+}  // namespace cppgc
+
 enum XFA_VERSION {
   XFA_VERSION_UNKNOWN = 0,
   XFA_VERSION_200 = 200,
@@ -35,18 +51,6 @@
   XFA_VERSION_MAX = 400,
 };
 
-class CFXJSE_Engine;
-class CJS_Runtime;
-class CScript_DataWindow;
-class CScript_EventPseudoModel;
-class CScript_HostPseudoModel;
-class CScript_LayoutPseudoModel;
-class CScript_LogPseudoModel;
-class CScript_SignaturePseudoModel;
-class CXFA_FFNotify;
-class CXFA_Node;
-class CXFA_Object;
-
 class CXFA_Document final : public CXFA_NodeOwner {
  public:
   class LayoutProcessorIface {
@@ -77,6 +81,7 @@
   CFXJSE_Engine* GetScriptContext() const;
 
   CXFA_FFNotify* GetNotify() const { return notify_.Get(); }
+  cppgc::Heap* GetHeap() const;
   CXFA_LocaleMgr* GetLocaleMgr();
   CXFA_Object* GetXFAObject(XFA_HashCode wsNodeNameHash);
   CXFA_Node* GetNodeByID(CXFA_Node* pRoot, WideStringView wsID) const;