Add service registration for Mojo services defined under chrome/

chrome/browser/extensions/chrome_extension_web_contents_observer.h

Index: chrome/browser/extensions/chrome_extension_web_contents_observer.h
diff --git a/chrome/browser/extensions/chrome_extension_web_contents_observer.h b/chrome/browser/extensions/chrome_extension_web_contents_observer.h
index e50119984f276013694c2a0775832242b3d10d18..3a98075240bdf8f36fbdde890be8d6841c711e14 100644
--- a/chrome/browser/extensions/chrome_extension_web_contents_observer.h
+++ b/chrome/browser/extensions/chrome_extension_web_contents_observer.h
@@ -34,6 +34,8 @@ class ChromeExtensionWebContentsObserver
   void RenderViewCreated(content::RenderViewHost* render_view_host) override;
   bool OnMessageReceived(const IPC::Message& message,
                          content::RenderFrameHost* render_frame_host) override;
+  void RegisterMojoServices(content::RenderFrameHost* render_frame_host,

[mark a. foltz, 2015/03/27 20:24:11]

Usually observers don't expose methods to callers that side effect the thing
being observed...

Or maybe this should be OnRegisterMojoServices?

[Kevin M, 2015/03/27 22:42:37]

Moved this out of the WebContentsObserver overrides block, since this is
actually just overriding ExtensionWebContentsObserver's method.

This does indeed change the object being observed, but it's no different than
preexisting functionality. sammc@ might be able to comment on that decision.

I believe it should stay as RegisterMojoServices because the method itself is
what's doing the Mojo registration; it's not fired after the fact.

[Sam McNally, 2015/03/31 23:38:51]

This might be better off as a method in ExtensionsBrowserClient, to be called
from service_registration.cc.

[Kevin M, 2015/04/01 23:23:50]

Done, thanks for the suggestion.

+                            const Extension* extension) override;
 
   // Adds a message to the extensions ErrorConsole.
   void OnDetailedConsoleMessageAdded(const base::string16& message,