Disable direct write if font count in registry is greater than or equ…

…al to threshold (currently 1750).

[email protected], ananta, asvitkine, cpu, scottmg
BUG=421305

Review URL: https://codereview.chromium.org/667013003

Cr-Commit-Position: refs/heads/master@{#300345}
(cherry picked from commit e2607d4)

Conflicts:
	ui/gfx/win/direct_write.cc

Review URL: https://codereview.chromium.org/671743002

Cr-Commit-Position: refs/branch-heads/2125@{#583}
Cr-Branched-From: b68026d-refs/heads/master@{#290040}

content/common/sandbox_win.cc

@@ -18,6 +18,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/win/iat_patch_function.h"
+#include "base/win/registry.h"
 #include "base/win/scoped_handle.h"
 #include "base/win/scoped_process_information.h"
 #include "base/win/windows_version.h"
@@ -603,6 +604,20 @@ bool ShouldUseDirectWrite() {
     return true;
 #endif
 
+  // We have logic in renderer_font_platform_win.cc for falling back to safe
+  // font list if machine has more than 1750 fonts installed. Users have
+  // complained about this as safe font list is usually not sufficient.
+  // We now disable direct write (gdi) if we encounter more number
+  // of fonts than a threshold (currently 1750).
+  // Refer: crbug.com/421305
+  const wchar_t kWindowsFontsRegistryKey[] =
+      L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Fonts";
+  base::win::RegistryValueIterator reg_iterator(HKEY_LOCAL_MACHINE,
+                                                kWindowsFontsRegistryKey);
+  const DWORD kMaxAllowedFontsBeforeFallbackToGDI = 1750;
+  if (reg_iterator.ValueCount() >= kMaxAllowedFontsBeforeFallbackToGDI)
+    return false;
+
   // Otherwise, check the field trial.
   const std::string group_name =
       base::FieldTrialList::FindFullName("DirectWrite");