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..4feaae2a0d6b915591c9f7d899d223d43f7bfba8 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
@@ -60,16 +60,27 @@ void CreateDirectWriteFactory(IDWriteFactory** factory) {
       reinterpret_cast<IUnknown**>(factory))));
 }
 
+// Needed as a function for Bind()
+IPC::Sender* GetSenderOverride() {
+  return g_sender_override;
+}
+
 }  // namespace
 
-void InitializeDWriteFontProxy() {
+void InitializeDWriteFontProxy(
+    const base::Callback<IPC::Sender*(void)>& sender) {
   mswr::ComPtr<IDWriteFactory> factory;
 
   CreateDirectWriteFactory(&factory);
 
   if (!g_font_collection) {
-    mswr::MakeAndInitialize<DWriteFontCollectionProxy>(
-        &g_font_collection, factory.Get(), g_sender_override);
+    if (g_sender_override) {
+      mswr::MakeAndInitialize<DWriteFontCollectionProxy>(
+          &g_font_collection, factory.Get(), base::Bind(&GetSenderOverride));
+    } else {
+      mswr::MakeAndInitialize<DWriteFontCollectionProxy>(&g_font_collection,
+                                                         factory.Get(), sender);
+    }
   }
 
   mswr::ComPtr<IDWriteFontFallback> font_fallback;