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

chrome/browser/ui/webui/mojo_web_ui_controller.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/mojo_web_ui_controller.h"
 
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/webui/mojo_web_ui_handler.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_ui_data_source.h"
 #include "content/public/common/bindings_policy.h"
+#include "content/public/common/service_registry.h"
 #include "mojo/public/cpp/system/core.h"
 
 MojoWebUIController::MojoWebUIController(content::WebUI* contents)
-    : WebUIController(contents),
-      mojo_data_source_(NULL) {
+    : WebUIController(contents), mojo_data_source_(NULL), weak_factory_(this) {
 }
 
 MojoWebUIController::~MojoWebUIController() {
 }
 
 void MojoWebUIController::RenderViewCreated(
     content::RenderViewHost* render_view_host) {
   render_view_host->AllowBindings(content::BINDINGS_POLICY_WEB_UI);
-
-  mojo::MessagePipe pipe;
-  ui_handler_ = CreateUIHandler(pipe.handle0.Pass());
-  render_view_host->SetWebUIHandle(pipe.handle1.Pass());
+  render_view_host->GetProcess()->ActivateMojo();
+  render_view_host->GetMainFrame()->GetServiceRegistry()->AddService(
+      "webui_controller",

[darin (slow to review), 2014/06/12 05:27:12]

perhaps instead of binding a generic "webui_controller" service, we should be
using the name of the Mojom-defined interface the webui page is intended to talk
to? e.g., "OmniboxUIHandlerMojo"

speaking of which, perhaps some HTML / JS files need to be updated to make
about:omnibox work with these changes?

[Sam McNally, 2014/06/12 08:56:40]

I'm planning to change it to use the auto-generated interface names in a
follow-up CL. Currently, the renderer side of the connection is set up in C++
(which doesn't know which interface the JS will want to connect to) and only the
handle is passed into the JS code. My plan is to make GetInterface available
from JS so the JS code will be able to connect directly to the browser-side
controller.

+      base::Bind(&MojoWebUIController::CreateAndStoreUIHandler,
+                 weak_factory_.GetWeakPtr()));
 }
 
 void MojoWebUIController::AddMojoResourcePath(const std::string& path,
                                               int resource_id) {
   if (!mojo_data_source_) {
     mojo_data_source_ = content::WebUIDataSource::AddMojoDataSource(
         Profile::FromWebUI(web_ui()));
   }
   mojo_data_source_->AddResourcePath(path, resource_id);
 }
+
+void MojoWebUIController::CreateAndStoreUIHandler(
+    mojo::ScopedMessagePipeHandle handle) {
+  ui_handler_ = CreateUIHandler(handle.Pass());
+}