Remove unused header from fx_system.h.

At one point, fx_system.h included safe_conversions.h for checked_cast()
calls. Those are gone now, so remove the #include and do IWYU for the
rest of the code base.

Change-Id: I5ae17046333b74ac4acc055b21f56e89c20013b3
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/70915
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp b/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp
index 9a7eddc..8a66c85 100644
--- a/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp
+++ b/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp
@@ -12,6 +12,7 @@
 #include "core/fpdfapi/parser/cpdf_reference.h"
 #include "core/fpdfapi/parser/cpdf_syntax_parser.h"
 #include "core/fpdfapi/parser/fpdf_parser_utility.h"
+#include "third_party/base/numerics/safe_conversions.h"
 
 namespace {
 
diff --git a/core/fpdfapi/render/cpdf_imagecacheentry.cpp b/core/fpdfapi/render/cpdf_imagecacheentry.cpp
index 9513a81..47aba7c 100644
--- a/core/fpdfapi/render/cpdf_imagecacheentry.cpp
+++ b/core/fpdfapi/render/cpdf_imagecacheentry.cpp
@@ -19,6 +19,7 @@
 #include "core/fpdfapi/render/cpdf_rendercontext.h"
 #include "core/fpdfapi/render/cpdf_renderstatus.h"
 #include "core/fxge/dib/cfx_dibitmap.h"
+#include "third_party/base/numerics/safe_conversions.h"
 
 namespace {
 
diff --git a/core/fxcrt/fx_system.h b/core/fxcrt/fx_system.h
index 135116c..1798c35 100644
--- a/core/fxcrt/fx_system.h
+++ b/core/fxcrt/fx_system.h
@@ -87,8 +87,6 @@
 #ifdef __cplusplus
 }  // extern "C"
 
-#include "third_party/base/numerics/safe_conversions.h"
-
 // Overloaded functions for C++ templates
 inline size_t FXSYS_len(const char* ptr) {
   return strlen(ptr);
diff --git a/core/fxge/android/cfpf_skiafont.cpp b/core/fxge/android/cfpf_skiafont.cpp
index 1c4eece..6358b41 100644
--- a/core/fxge/android/cfpf_skiafont.cpp
+++ b/core/fxge/android/cfpf_skiafont.cpp
@@ -13,6 +13,7 @@
 #include "core/fxge/android/cfpf_skiafontmgr.h"
 #include "core/fxge/android/cfpf_skiapathfont.h"
 #include "core/fxge/fx_freetype.h"
+#include "third_party/base/numerics/safe_conversions.h"
 
 #define FPF_EM_ADJUST(em, a) (em == 0 ? (a) : (a)*1000 / em)
 
diff --git a/fxjs/xfa/cjx_tree.cpp b/fxjs/xfa/cjx_tree.cpp
index e03fe83..6095da0 100644
--- a/fxjs/xfa/cjx_tree.cpp
+++ b/fxjs/xfa/cjx_tree.cpp
@@ -12,6 +12,7 @@
 #include "fxjs/js_resources.h"
 #include "fxjs/xfa/cfxjse_engine.h"
 #include "fxjs/xfa/cfxjse_value.h"
+#include "third_party/base/numerics/safe_conversions.h"
 #include "xfa/fxfa/parser/cxfa_arraynodelist.h"
 #include "xfa/fxfa/parser/cxfa_attachnodelist.h"
 #include "xfa/fxfa/parser/cxfa_document.h"