Allow app_shell embedders to override extensions client interfaces

extensions/shell/renderer/shell_content_renderer_client.h

Index: extensions/shell/renderer/shell_content_renderer_client.h
diff --git a/extensions/shell/renderer/shell_content_renderer_client.h b/extensions/shell/renderer/shell_content_renderer_client.h
index 6f623986cdcd2044440ef0b522e027d2d21d4711..b86fa0e9e9babaac42adf5644626361495c2cdef 100644
--- a/extensions/shell/renderer/shell_content_renderer_client.h
+++ b/extensions/shell/renderer/shell_content_renderer_client.h
@@ -14,7 +14,7 @@ namespace extensions {
 
 class Dispatcher;
 class DispatcherDelegate;
-class ShellExtensionsClient;
+class ExtensionsClient;
 class ShellExtensionsRendererClient;
 class ShellRendererMainDelegate;
 
@@ -52,8 +52,13 @@ class ShellContentRendererClient : public content::ContentRendererClient {
       const std::string& mime_type,
       const GURL& original_url) override;
 
+ protected:
+  // app_shell embedders may need custom extensions client interfaces.
+  // This class takes ownership of the returned object.
+  virtual ExtensionsClient* CreateExtensionsClient();
+
  private:
-  scoped_ptr<ShellExtensionsClient> extensions_client_;
+  scoped_ptr<ExtensionsClient> extensions_client_;
   scoped_ptr<ShellExtensionsRendererClient> extensions_renderer_client_;
   scoped_ptr<DispatcherDelegate> extension_dispatcher_delegate_;
   scoped_ptr<Dispatcher> extension_dispatcher_;