Add namespace and re-arrange PDFium's local copy of chromium /base.

fpdfsdk/src/fpdfview.cpp

Index: fpdfsdk/src/fpdfview.cpp
diff --git a/fpdfsdk/src/fpdfview.cpp b/fpdfsdk/src/fpdfview.cpp
index fba5d65bcecfbdec3b9cec470f0b62dd4363e45f..8a317529751c7a1b45986ce9db6fa19bc6575c5c 100644
--- a/fpdfsdk/src/fpdfview.cpp
+++ b/fpdfsdk/src/fpdfview.cpp
@@ -10,7 +10,7 @@
 #include "../include/fsdk_rendercontext.h"
 #include "../include/fpdf_progressive.h"
 #include "../include/fpdf_ext.h"
-#include "../../third_party/numerics/safe_conversions_impl.h"
+#include "../../third_party/base/numerics/safe_conversions_impl.h"
 
 CPDF_CustomAccess::CPDF_CustomAccess(FPDF_FILEACCESS* pFileAccess)
 {
@@ -23,7 +23,7 @@ FX_BOOL CPDF_CustomAccess::ReadBlock(void* buffer, FX_FILESIZE offset, size_t si
     if (offset < 0) {
         return FALSE;
     }
-    FX_SAFE_FILESIZE newPos = base::checked_cast<FX_FILESIZE, size_t>(size);
+    FX_SAFE_FILESIZE newPos = third_party::base::checked_cast<FX_FILESIZE, size_t>(size);
     newPos += offset;
     if (!newPos.IsValid() || newPos.ValueOrDie() > m_FileAccess.m_FileLen) {
         return FALSE;
@@ -209,7 +209,7 @@ public:
             if (offset < 0) {
                 return FALSE;
             }
-            FX_SAFE_FILESIZE newPos = base::checked_cast<FX_FILESIZE, size_t>(size);
+            FX_SAFE_FILESIZE newPos = third_party::base::checked_cast<FX_FILESIZE, size_t>(size);
             newPos += offset;
             if (!newPos.IsValid() || newPos.ValueOrDie() > (FX_DWORD)m_size) {
                 return FALSE;