Creating PNG images from web content to be used by OverviewMode navigation

athena/activity/public/activity_view_model.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ATHENA_ACTIVITY_PUBLIC_ACTIVITY_VIEW_MODEL_H_
 #define ATHENA_ACTIVITY_PUBLIC_ACTIVITY_VIEW_MODEL_H_
 
 #include "athena/athena_export.h"
 #include "base/strings/string16.h"
 
@@ skipping 38 matching lines @@
   // loaded. Note that the caller should not hold on to the view since it can
   // be deleted by the resource manager.
   virtual views::View* GetContentsView() = 0;
 
   // Creates a custom widget for the activity. Returns NULL to use default
   // implementation.
   virtual views::Widget* CreateWidget() = 0;
 
   // Returns an image which can be used to represent the activity in e.g. the
   // overview mode. The returned image can have no size if either a view exists
-  // or the activity has not yet been loaded. In that case
-  // GetRepresentativeColor() should be used to clear the preview area.
-  // Note: We intentionally do not use a layer / view for this.
+  // or the activity has not yet been loaded or ever been presented. In that
+  // case GetRepresentativeColor() should be used to clear the preview area.
+  // Note that since the image gets created upon request, and the
+  // ActivityViewModel will hold no reference to the returned image data. As
+  // such it is advisable to hold on to the image as long as needed instead of
+  // calling this function frequently since it will cause time to generate.
   virtual gfx::ImageSkia GetOverviewModeImage() = 0;
 
   // Prepares the contents view for overview.
   virtual void PrepareContentsForOverview() = 0;
 
   // Undoes any changes done by PrepareContentsForOverview().
   virtual void ResetContentsView() = 0;
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_ACTIVITY_PUBLIC_ACTIVITY_VIEW_MODEL_H_