Support exposing Mojo services between render frames, render threads, and their respective hosts.

content/public/renderer/render_thread.h

Index: content/public/renderer/render_thread.h
diff --git a/content/public/renderer/render_thread.h b/content/public/renderer/render_thread.h
index a545150f9bb01b1286f4d049a603a49747a926bf..695f1fd7573184fd14b8edba72c6c78cc833577f 100644
--- a/content/public/renderer/render_thread.h
+++ b/content/public/renderer/render_thread.h
@@ -39,6 +39,7 @@ namespace content {
 
 class RenderProcessObserver;
 class ResourceDispatcherDelegate;
+class ServiceRegistry;
 
 class CONTENT_EXPORT RenderThread : public IPC::Sender {
  public:
@@ -136,6 +137,9 @@ class CONTENT_EXPORT RenderThread : public IPC::Sender {
   // Release cached font.
   virtual void ReleaseCachedFonts() = 0;
 #endif
+
+  // Returns the ServiceRegistry for this thread.
+  virtual ServiceRegistry* GetServiceRegistry() = 0;
 };
 
 }  // namespace content