Use ChildThreadImpl::thread_safe_sender in font proxy if available

content/child/dwrite_font_proxy/dwrite_font_proxy_init_win.cc

Index: content/child/dwrite_font_proxy/dwrite_font_proxy_init_win.cc
diff --git a/content/child/dwrite_font_proxy/dwrite_font_proxy_init_win.cc b/content/child/dwrite_font_proxy/dwrite_font_proxy_init_win.cc
index da083233fb2f7fccb082bb85c9d33e77b69249e9..7a9a9efef80a0f36e49101e4e566929a76ef30df 100644
--- a/content/child/dwrite_font_proxy/dwrite_font_proxy_init_win.cc
+++ b/content/child/dwrite_font_proxy/dwrite_font_proxy_init_win.cc
@@ -11,9 +11,11 @@
 #include "base/debug/alias.h"
 #include "base/win/iat_patch_function.h"
 #include "base/win/windows_version.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/dwrite_font_proxy/dwrite_font_proxy_win.h"
 #include "content/child/dwrite_font_proxy/font_fallback_win.h"
 #include "content/child/font_warmup_win.h"
+#include "content/child/thread_safe_sender.h"
 #include "skia/ext/fontmgr_default_win.h"
 #include "third_party/WebKit/public/web/win/WebFontRendering.h"
 #include "third_party/skia/include/ports/SkFontMgr.h"
@@ -74,9 +76,17 @@ void InitializeDWriteFontProxy() {
 
   mswr::ComPtr<IDWriteFontFallback> font_fallback;
   mswr::ComPtr<IDWriteFactory2> factory2;
+  IPC::Sender* sender = g_sender_override;
+
+  // Hack for crbug.com/631254: set the sender if we can get one, so that when

[jam, 2016/07/28 22:04:43]

nit: saying hack makes it sound like this should be fixed properly. using
thread-safe sender is a standard pattern.

I would just get rid of this comment since it's documenting what the code is
doing.

[Ilya Kulshin, 2016/07/28 22:10:41]

This should be fixed properly. One possible fix we are talking about is to
detect when the pepper font api is being called from the wrong thread, and
marshal the call to the appropriate thread.

[jam, 2016/07/29 22:34:58]

I don't understand this comment. That's what the SafeSender is doing internally?

+  // Flash calls into the font proxy from a different thread we will have a
+  // sender available.
+  if (!sender && ChildThreadImpl::current())

[jam, 2016/07/28 22:04:43]

are you sure you need the ChildThreadImpl::current() check?

[Ilya Kulshin, 2016/07/28 22:10:41]

Yes, otherwise it crashes in the renderer because ChildThreadImpl::current()
returns null at the time this code is initialized.

+    sender = ChildThreadImpl::current()->thread_safe_sender();
+
   if (SUCCEEDED(factory.As(&factory2)) && factory2.Get()) {
     mswr::MakeAndInitialize<FontFallback>(
-        &font_fallback, g_font_collection.Get(), g_sender_override);
+        &font_fallback, g_font_collection.Get(), sender);
   }
 
   sk_sp<SkFontMgr> skia_font_manager(SkFontMgr_New_DirectWrite(