cc: Call PrepareTiles when becoming visible in browser only.

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <set>
@@ skipping 1970 matching lines @@
   DidVisibilityChange(this, visible_);
   UpdateTileManagerMemoryPolicy(ActualManagedMemoryPolicy());
 
   // If we just became visible, we have to ensure that we draw high res tiles,
   // to prevent checkerboard/low res flashes.
   if (visible_)
     SetRequiresHighResToDraw();
   else
     EvictAllUIResources();
 
-  // Call PrepareTiles unconditionally on visibility change since this tab may
-  // never get another draw or timer tick. When becoming visible we care about
-  // unblocking the scheduler which might be waiting for activation / ready to
-  // draw. When becoming invisible we care about evicting tiles immediately.
-  PrepareTiles();
+  // PrepareTiles when becoming invisible so that we evict tiles immediately.
+  if (!visible_)
+    PrepareTiles();
 
   if (!renderer_)
     return;
 
   renderer_->SetVisible(visible);
 }
 
 void LayerTreeHostImpl::SetNeedsAnimate() {
   NotifySwapPromiseMonitorsOfSetNeedsRedraw();
   client_->SetNeedsAnimateOnImplThread();
@@ skipping 1607 matching lines @@
   if (active_tree()) {
     LayerAnimationValueProvider* layer = active_tree()->LayerById(layer_id);
     if (layer)
       return layer->ScrollOffsetForAnimation();
   }
 
   return gfx::ScrollOffset();
 }
 
 }  // namespace cc