Update Webview Webkit preferences

Whenever we create a RenderViewHost, update it's Blink properties and
enable the scrollbar.

The scrollbar is disabled by default on Chromecast since Cast Apps are
not supposed to be scrollable. Webviews don't have such limitations so
enable scrollbars for Webviews only.

BUG=b/158124105
TEST=Manually on device with a scrollable page.

Change-Id: I0e7c8971760977568afa2a6a3eede6b28a8dd6e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2231589
Reviewed-by: Albert Chaulk <achaulk@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776157}

chromecast/browser/webview/web_content_controller.h

@@ -64,6 +64,17 @@ class WebContentController
   void AttachTo(aura::Window* window, int window_id);
 
  protected:
+  // content::WebContentsObserver
+  void RenderFrameCreated(content::RenderFrameHost* render_frame_host) override;
+  void RenderFrameDeleted(content::RenderFrameHost* render_frame_host) override;
+  void RenderFrameHostChanged(content::RenderFrameHost* old_host,
+                              content::RenderFrameHost* new_host) override;
+  void MainFrameWasResized(bool width_changed) override;
+  void FrameSizeChanged(content::RenderFrameHost* render_frame_host,
+                        const gfx::Size& frame_size) override;
+  void RenderViewCreated(content::RenderViewHost* render_view_host) override;
+  void RenderViewDeleted(content::RenderViewHost* render_view_host) override;
+
   static void RegisterRenderWidgetInputObserverFromRenderFrameHost(
       WebContentController* web_content_controller,
       content::RenderFrameHost* render_frame_host);
@@ -111,17 +122,6 @@ class WebContentController
   // exo::SurfaceObserver
   void OnSurfaceDestroying(exo::Surface* surface) override;
 
-  // content::WebContentsObserver
-  void RenderFrameCreated(content::RenderFrameHost* render_frame_host) override;
-  void RenderFrameDeleted(content::RenderFrameHost* render_frame_host) override;
-  void RenderFrameHostChanged(content::RenderFrameHost* old_host,
-                              content::RenderFrameHost* new_host) override;
-  void MainFrameWasResized(bool width_changed) override;
-  void FrameSizeChanged(content::RenderFrameHost* render_frame_host,
-                        const gfx::Size& frame_size) override;
-  void RenderViewCreated(content::RenderViewHost* render_view_host) override;
-  void RenderViewDeleted(content::RenderViewHost* render_view_host) override;
-
   // JsClientInstance::Observer
   void OnJsClientInstanceRegistered(int process_id,
                                     int routing_id,

chromecast/browser/webview/webview_controller.cc

@@ -42,6 +42,14 @@ class WebviewUserData : public base::SupportsUserData::Data {
   WebviewController* controller_;
 };
 
+void UpdateWebkitPreferences(content::RenderViewHost* render_view_host) {
+  content::WebPreferences prefs = render_view_host->GetWebkitPreferences();
+  // Allow Webviews to show scrollbars. These are globally disabled since Cast
+  // Apps are not expected to be scrollable.
+  prefs.hide_scrollbars = false;
+  render_view_host->UpdateWebkitPreferences(prefs);
+}
+
 }  // namespace
 
 WebviewController::WebviewController(content::BrowserContext* browser_context,
@@ -165,6 +173,12 @@ void WebviewController::DidFirstVisuallyNonEmptyPaint() {
   }
 }
 
+void WebviewController::RenderViewCreated(
+    content::RenderViewHost* render_view_host) {
+  WebContentController::RenderViewCreated(render_view_host);
+  UpdateWebkitPreferences(render_view_host);
+}
+
 void WebviewController::SendNavigationEvent(
     WebviewNavigationThrottle* throttle,
     content::NavigationHandle* navigation_handle) {

chromecast/browser/webview/webview_controller.h

@@ -80,6 +80,9 @@ class WebviewController : public CastWebContents::Delegate,
   // content::WebContentsObserver
   void DidFirstVisuallyNonEmptyPaint() override;
 
+  // WebContentController
+  void RenderViewCreated(content::RenderViewHost* render_view_host) override;
+
   const bool enabled_for_dev_;
   std::unique_ptr<content::WebContents> contents_;
   std::unique_ptr<CastWebContents> cast_web_contents_;