Add a Javascript wrapper around ServiceRegistry and expose it to WebUI.

content/public/common/service_registry.h

Index: content/public/common/service_registry.h
diff --git a/content/public/common/service_registry.h b/content/public/common/service_registry.h
index f35bad4c1b23029075a77a3d19f21a245d196895..64ec5bd5e2cbb8c7148baea9241d31054a5ce99f 100644
--- a/content/public/common/service_registry.h
+++ b/content/public/common/service_registry.h
@@ -9,6 +9,7 @@
 
 #include "base/bind.h"
 #include "base/callback.h"
+#include "base/memory/weak_ptr.h"
 #include "base/strings/string_piece.h"
 #include "content/common/content_export.h"
 #include "mojo/public/cpp/bindings/interface_ptr.h"
@@ -58,6 +59,8 @@ class CONTENT_EXPORT ServiceRegistry {
   virtual void GetRemoteInterface(const base::StringPiece& name,
                                   mojo::ScopedMessagePipeHandle handle) = 0;
 
+  virtual base::WeakPtr<ServiceRegistry> GetWeakPtr() = 0;
+
  private:
   template <typename Interface>
   static void ForwardToServiceFactory(