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

chrome/browser/ui/webui/mojo_web_ui_controller.cc

Index: chrome/browser/ui/webui/mojo_web_ui_controller.cc
diff --git a/chrome/browser/ui/webui/mojo_web_ui_controller.cc b/chrome/browser/ui/webui/mojo_web_ui_controller.cc
index 04ba05f3ec4b9a7827d4a415856870cfd047bb90..25256bbc6610eeff4d1032fa00b74dc674e2c9a4 100644
--- a/chrome/browser/ui/webui/mojo_web_ui_controller.cc
+++ b/chrome/browser/ui/webui/mojo_web_ui_controller.cc
@@ -6,14 +6,16 @@
 
 #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() {
@@ -22,10 +24,11 @@ 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,
@@ -36,3 +39,8 @@ void MojoWebUIController::AddMojoResourcePath(const std::string& path,
   }
   mojo_data_source_->AddResourcePath(path, resource_id);
 }
+
+void MojoWebUIController::CreateAndStoreUIHandler(
+    mojo::ScopedMessagePipeHandle handle) {
+  ui_handler_ = CreateUIHandler(handle.Pass());
+}