cc: Set requires high res upon becoming visible

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 "base/basictypes.h"
@@ skipping 1719 matching lines @@
 
 void LayerTreeHostImpl::SetVisible(bool visible) {
   DCHECK(proxy_->IsImplThread());
 
   if (visible_ == visible)
     return;
   visible_ = visible;
   DidVisibilityChange(this, visible_);
   EnforceManagedMemoryPolicy(ActualManagedMemoryPolicy());
 
-  if (!visible_) {
+  // If we just became visible, we have to ensure that we draw high res tiles,
+  // to prevent checkerboard/low res flashes.
+  if (visible_)
     active_tree()->SetRequiresHighResToDraw();

[enne (OOO), 2014/05/13 18:21:53]

I was originally going to suggest that maybe we set this flag on both trees when
not visible.

However, I think this is slightly better because it means we could have a fast
activation when not visible and there are no resources.  (Maybe we consider
auto-activating when not visible, honestly.)

[danakj, 2014/05/13 18:23:13]

Or when becoming visible. +1 to that either way.

+  else
     EvictAllUIResources();
-  }
 
   // Evict tiles immediately if invisible since this tab may never get another
   // draw or timer tick.
   if (!visible_)
     ManageTiles();
 
   if (!renderer_)
     return;
 
   renderer_->SetVisible(visible);
@@ skipping 1363 matching lines @@
   swap_promise_monitor_.erase(monitor);
 }
 
 void LayerTreeHostImpl::NotifySwapPromiseMonitorsOfSetNeedsRedraw() {
   std::set<SwapPromiseMonitor*>::iterator it = swap_promise_monitor_.begin();
   for (; it != swap_promise_monitor_.end(); it++)
     (*it)->OnSetNeedsRedrawOnImpl();
 }
 
 }  // namespace cc