<webview>: Zooming the embedder should zoom the guest by the same level.

Note: Currently this solution is implemented in the chrome module but once
ZoomController moves to extensions, zooming from embedder to guest should
move to GuestViewBase and a more general solution should be made available
for GuestView types that wish to receive this zoom plumbing.

BUG=416581

Review URL: https://codereview.chromium.org/598163003

Cr-Commit-Position: refs/heads/master@{#296540}

chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.cc

@@ -123,6 +123,20 @@ void ChromeWebViewGuestDelegate::OnEmbedderDestroyed() {
           web_view_guest()->view_instance_id()));
 }
 
+void ChromeWebViewGuestDelegate::OnDidAttachToEmbedder() {
+  // TODO(fsamuel): This code should be implemented in GuestViewBase once the
+  // ZoomController moves to the extensions module.
+  ZoomController* zoom_controller = ZoomController::FromWebContents(
+      web_view_guest()->embedder_web_contents());
+  if (!zoom_controller)
+    return;
+  // Listen to the embedder's zoom changes.
+  zoom_controller->AddObserver(this);
+  // Set the guest's initial zoom level to be equal to the embedder's.
+  ZoomController::FromWebContents(guest_web_contents())->
+      SetZoomLevel(zoom_controller->GetZoomLevel());
+}
+
 void ChromeWebViewGuestDelegate::OnDidCommitProvisionalLoadForFrame(
     bool is_main_frame) {
   // Update the current zoom factor for the new page.
@@ -238,3 +252,9 @@ void ChromeWebViewGuestDelegate::OnAccessibilityStatusChanged(
   }
 }
 #endif
+
+void ChromeWebViewGuestDelegate::OnZoomChanged(
+    const ZoomController::ZoomChangedEventData& data) {
+  ZoomController::FromWebContents(guest_web_contents())->
+      SetZoomLevel(data.new_zoom_level);
+}

chrome/browser/guest_view/web_view/chrome_web_view_guest_delegate.h

@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_GUEST_VIEW_WEB_VIEW_CHROME_WEB_VIEW_GUEST_DELEGATE_H_
 
 #include "chrome/browser/extensions/api/web_view/chrome_web_view_internal_api.h"
+#include "chrome/browser/ui/zoom/zoom_observer.h"
 #include "extensions/browser/guest_view/web_view/web_view_guest.h"
 #include "extensions/browser/guest_view/web_view/web_view_guest_delegate.h"
 
@@ -19,7 +20,8 @@ namespace ui {
 class SimpleMenuModel;
 }  // namespace ui
 
-class ChromeWebViewGuestDelegate : public extensions::WebViewGuestDelegate {
+class ChromeWebViewGuestDelegate : public extensions::WebViewGuestDelegate,
+                                   public ZoomObserver {
  public :
   explicit ChromeWebViewGuestDelegate(
       extensions::WebViewGuest* web_view_guest);
@@ -31,6 +33,7 @@ class ChromeWebViewGuestDelegate : public extensions::WebViewGuestDelegate {
       const content::ContextMenuParams& params) OVERRIDE;
   virtual void OnAttachWebViewHelpers(content::WebContents* contents) OVERRIDE;
   virtual void OnEmbedderDestroyed() OVERRIDE;
+  virtual void OnDidAttachToEmbedder() OVERRIDE;
   virtual void OnDidCommitProvisionalLoadForFrame(bool is_main_frame) OVERRIDE;
   virtual void OnDidInitialize() OVERRIDE;
   virtual void OnDocumentLoadedInFrame(
@@ -41,6 +44,10 @@ class ChromeWebViewGuestDelegate : public extensions::WebViewGuestDelegate {
       int request_id,
       const MenuItemVector* items) OVERRIDE;
 
+  // ZoomObserver implementation.
+  virtual void OnZoomChanged(
+      const ZoomController::ZoomChangedEventData& data) OVERRIDE;
+
   extensions::WebViewGuest* web_view_guest() const { return web_view_guest_; }
 
  private:

extensions/browser/guest_view/web_view/web_view_guest.cc

@@ -301,6 +301,9 @@ void WebViewGuest::DidAttachToEmbedder() {
   // We need to set the background opaque flag after navigation to ensure that
   // there is a RenderWidgetHostView available.
   SetAllowTransparency(allow_transparency);
+
+  if (web_view_guest_delegate_)
+    web_view_guest_delegate_->OnDidAttachToEmbedder();
 }
 
 void WebViewGuest::DidInitialize() {

extensions/browser/guest_view/web_view/web_view_guest_delegate.h

@@ -43,6 +43,10 @@ class WebViewGuestDelegate {
   // Called to perform some cleanup prior to destruction.
   virtual void OnEmbedderDestroyed() = 0;
 
+  // Called after the guest has been attached to an embedder and suspended
+  // resource loads have been resumed.
+  virtual void OnDidAttachToEmbedder() = 0;
+
   // Called when the guest WebContents commits a provisional load in any frame.
   virtual void OnDidCommitProvisionalLoadForFrame(bool is_main_frame) = 0;