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

content/renderer/web_ui_mojo.cc

Index: content/renderer/web_ui_mojo.cc
diff --git a/content/renderer/web_ui_mojo.cc b/content/renderer/web_ui_mojo.cc
index 38c71d5c1c6574b3e7383701b26e29cf1b313267..b87790c15ad2d84cb793e5aa5ad06b46608023a6 100644
--- a/content/renderer/web_ui_mojo.cc
+++ b/content/renderer/web_ui_mojo.cc
@@ -5,6 +5,7 @@
 #include "content/renderer/web_ui_mojo.h"
 
 #include "content/common/view_messages.h"
+#include "content/public/common/service_registry.h"
 #include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_view.h"
 #include "content/renderer/web_ui_mojo_context_state.h"
@@ -84,8 +85,11 @@ void WebUIMojo::DestroyContextState(v8::Handle<v8::Context> context) {
 
 void WebUIMojo::OnDidFinishDocumentLoad() {
   did_finish_document_load_ = true;
-  if (pending_handle_.is_valid())
-    SetHandleOnContextState(pending_handle_.Pass());
+  mojo::MessagePipe pipe;
+  SetHandleOnContextState(pipe.handle0.Pass());
+  RenderFrame::FromWebFrame(render_view()->GetWebView()->mainFrame())
+      ->GetServiceRegistry()

[darin (slow to review), 2014/06/21 04:33:35]

nit: "Wrap after binary operators, not before." from
http://dev.chromium.org/developers/coding-style

RenderFrame::FromWebFrame(...)->
    GetServiceRegistry()->
        GetRemoteInterface(...);

[Sam McNally, 2014/06/24 04:00:29]

Done.

+      ->GetRemoteInterface("webui_controller", pipe.handle1.Pass());
 }
 
 void WebUIMojo::SetHandleOnContextState(mojo::ScopedMessagePipeHandle handle) {