Enable pinch-zoom on the new login page.

extensions/browser/guest_view/web_view/web_view_guest.h

Index: extensions/browser/guest_view/web_view/web_view_guest.h
diff --git a/extensions/browser/guest_view/web_view/web_view_guest.h b/extensions/browser/guest_view/web_view/web_view_guest.h
index 2e399ea92c3e057e99c1537674875f4f243e8aa3..8617c8e8de146dc6a0cc566997524216bdb94c1b 100644
--- a/extensions/browser/guest_view/web_view/web_view_guest.h
+++ b/extensions/browser/guest_view/web_view/web_view_guest.h
@@ -79,6 +79,8 @@ class WebViewGuest : public GuestView<WebViewGuest>,
   // Set the zoom factor.
   void SetZoom(double zoom_factor);
 
+  void SetAllowScaling(bool allow);
+
   // Sets the transparency of the guest.
   void SetAllowTransparency(bool allow);
 
@@ -126,6 +128,8 @@ class WebViewGuest : public GuestView<WebViewGuest>,
   void HandleKeyboardEvent(
       content::WebContents* source,
       const content::NativeWebKeyboardEvent& event) override;
+  bool PreHandleGestureEvent(content::WebContents* source,
+                             const blink::WebGestureEvent& event) override;
   void RendererResponsive(content::WebContents* source) override;
   void RendererUnresponsive(content::WebContents* source) override;
   void RequestMediaAccessPermission(
@@ -362,6 +366,9 @@ class WebViewGuest : public GuestView<WebViewGuest>,
   // Stores the current zoom factor.
   double current_zoom_factor_;
 
+  // Determines if this guest accepts pinch-zoom gestures.
+  bool allow_scaling_;
+
   // This is used to ensure pending tasks will not fire after this object is
   // destroyed.
   base::WeakPtrFactory<WebViewGuest> weak_ptr_factory_;