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

content/common/font_warmup_win.cc

Index: content/common/font_warmup_win.cc
diff --git a/content/common/font_warmup_win.cc b/content/common/font_warmup_win.cc
index f9825fef0c734f36243cd7be4259db2e596b8a1f..73f5dbb06c424ca0d13774e8b0f9bd28a5139a68 100644
--- a/content/common/font_warmup_win.cc
+++ b/content/common/font_warmup_win.cc
@@ -23,6 +23,7 @@
 #include "base/win/iat_patch_function.h"
 #include "base/win/windows_version.h"
 #include "content/public/common/dwrite_font_platform_win.h"
+#include "ppapi/shared_impl/proxy_lock.h"
 #include "skia/ext/fontmgr_default_win.h"
 #include "skia/ext/refptr.h"
 #include "third_party/WebKit/public/web/win/WebFontRendering.h"
@@ -255,6 +256,7 @@ skia::RefPtr<SkTypeface> GetTypefaceFromLOGFONT(const LOGFONTW* log_font) {
                                        : SkFontStyle::kUpright_Slant);
 
   std::string family_name = base::WideToUTF8(log_font->lfFaceName);
+  ppapi::ProxyAutoLock lock;  // Needed for DirectWrite font proxy.
   return skia::AdoptRef(
       g_warmup_fontmgr->matchFamilyStyle(family_name.c_str(), style));
 }
@@ -486,8 +488,12 @@ SkFontMgr* GetPreSandboxWarmupFontMgr() {
 }
 
 GdiFontPatchData* PatchGdiFontEnumeration(const base::FilePath& path) {
-  // We assume the fontmgr is already warmed up before calling this.
-  DCHECK(g_warmup_fontmgr);
+  if (content::ShouldUseDirectWriteFontProxyFieldTrial()) {

[fdoray, 2015/12/30 01:15:08]

// If the font cache is used, |g_warmup_fontmgr| is expected to be initialized
// by GetPreSandboxWarmupFontMgr before this function is called. If the font
// proxy is used, |g_warmup_fontmgr| is initialized when this function is
// called. This function is never called more than once per process.
if (content::ShouldUseDirectWriteFontProxyFieldTrial()) {
  DCHECK(!g_warmup_fontmgr);
  g_warmup_fontmgr = SkFontMgr_New_DirectWrite();
}
DCHECK(g_warmup_fontmgr);

Can you confirm that the comment I wrote is right? If PatchGdiFontEnumeration is
called multiple times, the previous value of |g_warmup_fontmgr| is leaked.

[Ilya Kulshin, 2015/12/30 01:59:46]

Good point about the leak. From tracing the code it looks like it's actually
called at least once per plugin, so I'll add a check to only initialize it if
it's not initialized already. 

+    g_warmup_fontmgr = SkFontMgr_New_DirectWrite();
+  } else {
+    // We assume the fontmgr is already warmed up before calling this.
+    DCHECK(g_warmup_fontmgr);
+  }
   return new GdiFontPatchDataImpl(path);
 }