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

content/test/layouttest_support.cc

Index: content/test/layouttest_support.cc
diff --git a/content/test/layouttest_support.cc b/content/test/layouttest_support.cc
index 0f4fe3b6ca6be0256a4e7d37cbe7ac83af1fb728..c99e56a2edee8aae87425bea646baeddab1ba30b 100644
--- a/content/test/layouttest_support.cc
+++ b/content/test/layouttest_support.cc
@@ -42,8 +42,10 @@
 #include "content/browser/frame_host/popup_menu_helper_mac.h"
 #elif defined(OS_WIN)
 #include "content/common/font_warmup_win.h"
+#include "content/public/common/dwrite_font_platform_win.h"
 #include "third_party/WebKit/public/web/win/WebFontRendering.h"
 #include "third_party/skia/include/ports/SkFontMgr.h"
+#include "third_party/skia/include/ports/SkTypeface_win.h"
 #include "ui/gfx/win/direct_write.h"
 #endif
 
@@ -104,7 +106,8 @@ void RegisterSideloadedTypefaces(SkFontMgr* fontmgr) {
        i != files.end();
        ++i) {
     SkTypeface* typeface = fontmgr->createFromFile(i->c_str());
-    DoPreSandboxWarmupForTypeface(typeface);
+    if (!ShouldUseDirectWriteFontProxyFieldTrial())
+      DoPreSandboxWarmupForTypeface(typeface);
     blink::WebFontRendering::addSideloadedFontForTesting(typeface);
   }
 }
@@ -174,8 +177,12 @@ void EnableRendererLayoutTestMode() {
   RenderThreadImpl::current()->set_layout_test_mode(true);
 
 #if defined(OS_WIN)
-  if (gfx::win::ShouldUseDirectWrite())
-    RegisterSideloadedTypefaces(GetPreSandboxWarmupFontMgr());
+  if (gfx::win::ShouldUseDirectWrite()) {
+    if (ShouldUseDirectWriteFontProxyFieldTrial())
+      RegisterSideloadedTypefaces(SkFontMgr_New_DirectWrite());
+    else
+      RegisterSideloadedTypefaces(GetPreSandboxWarmupFontMgr());
+  }
 #endif
 }