Add logic to switch to DirectWrite font proxy via field trial.

content/renderer/renderer_main_platform_delegate_win.cc

Index: content/renderer/renderer_main_platform_delegate_win.cc
diff --git a/content/renderer/renderer_main_platform_delegate_win.cc b/content/renderer/renderer_main_platform_delegate_win.cc
index 675961da16ca60e94ab6d7135f398a0053e78303..ae7e7e47f4b0e421ac90bc333d917e96e28d39d9 100644
--- a/content/renderer/renderer_main_platform_delegate_win.cc
+++ b/content/renderer/renderer_main_platform_delegate_win.cc
@@ -4,6 +4,8 @@
 
 #include "content/renderer/renderer_main_platform_delegate.h"
 
+#include <dwrite.h>
+
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ -11,8 +13,10 @@
 #include "base/win/scoped_comptr.h"
 #include "base/win/win_util.h"
 #include "base/win/windows_version.h"
+#include "content/child/dwrite_font_proxy/dwrite_font_proxy_init_win.h"
 #include "content/common/font_warmup_win.h"
 #include "content/public/common/content_switches.h"
+#include "content/public/common/dwrite_font_platform_win.h"
 #include "content/public/common/injection_test_win.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/renderer/render_thread_impl.h"
@@ -24,8 +28,6 @@
 #include "ui/gfx/win/direct_write.h"
 #include "ui/gfx/win/dpi.h"
 
-#include <dwrite.h>
-
 namespace content {
 namespace {
 
@@ -38,6 +40,12 @@ void SkiaPreCacheFont(const LOGFONT& logfont) {
   }
 }
 
+// Helper function to cast RenderThread to IPC::Sender so we can Bind()
+// it.
+IPC::Sender* GetRenderThreadSender() {
+  return RenderThread::Get();
+}
+
 }  // namespace
 
 RendererMainPlatformDelegate::RendererMainPlatformDelegate(
@@ -67,7 +75,10 @@ void RendererMainPlatformDelegate::PlatformInitialize() {
     scoped_ptr<icu::TimeZone> zone(icu::TimeZone::createDefault());
 
     if (use_direct_write) {
-      WarmupDirectWrite();
+      if (ShouldUseDirectWriteFontProxyFieldTrial())
+        InitializeDWriteFontProxy(base::Bind(&GetRenderThreadSender));
+      else
+        WarmupDirectWrite();
     } else {
       SkTypeface_SetEnsureLOGFONTAccessibleProc(SkiaPreCacheFont);
     }
@@ -77,6 +88,8 @@ void RendererMainPlatformDelegate::PlatformInitialize() {
 }
 
 void RendererMainPlatformDelegate::PlatformUninitialize() {
+  if (ShouldUseDirectWriteFontProxyFieldTrial())
+    UninitializeDWriteFontProxy();
 }
 
 bool RendererMainPlatformDelegate::EnableSandbox() {