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..28c9a8de96c845636277c2e50c9a24d152dc639c 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"
@@ -20,7 +21,8 @@ namespace content {
 // A ServiceRegistry exposes local services that have been added using
 // AddService to a paired remote ServiceRegistry and provides local access to
 // services exposed by the remote ServiceRegistry through GetInterface.
-class CONTENT_EXPORT ServiceRegistry {
+class CONTENT_EXPORT ServiceRegistry
+    : public base::SupportsWeakPtr<ServiceRegistry> {
  public:
   virtual ~ServiceRegistry() {}