cc: Throttle tile priority updates to once a frame.

cc/layer_tree_host_impl.cc

Index: cc/layer_tree_host_impl.cc
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 0b921d09290fd852d1f1a1789eb2be25746f624e..6eb28957cceb907000a65a812e7fee50fb878356 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -193,7 +193,7 @@ void LayerTreeHostImpl::commitComplete()
     // more lazily when needed prior to drawing.
     if (m_settings.implSidePainting) {
         pendingTree()->set_needs_update_draw_properties();
-        pendingTree()->UpdateDrawProperties();
+        pendingTree()->UpdateDrawProperties(LayerTreeImpl::UPDATE_PENDING_TREE);

[epenner, 2013/01/25 20:29:09]

Wouldn't it be easier to just call pendingTree()->CalculateTilePriorities()
after UpdateDrawProperties()?

If it's for performance reasons do we have any evidence it saves us time to save
one loop over the layers?

     } else {
         activeTree()->set_needs_update_draw_properties();
     }
@@ -650,7 +650,7 @@ bool LayerTreeHostImpl::prepareToDraw(FrameData& frame)
 
     if (m_topControlsManager)
         m_topControlsManager->UpdateDrawPositions();
-    activeTree()->UpdateDrawProperties();
+    activeTree()->UpdateDrawProperties(LayerTreeImpl::UPDATE_ACTIVE_TREE_FOR_DRAW);
 
     frame.renderSurfaceLayerList = &activeTree()->RenderSurfaceLayerList();
     frame.renderPasses.clear();
@@ -934,7 +934,7 @@ void LayerTreeHostImpl::activatePendingTreeIfNeeded()
     if (!pendingTree())
         return;
 
-    pendingTree()->UpdateDrawProperties();
+    pendingTree()->UpdateDrawProperties(LayerTreeImpl::UPDATE_PENDING_TREE);
 
     // It's always fine to activate to an empty tree.  Otherwise, only
     // activate once all visible resources in pending tree are ready.
@@ -1157,7 +1157,7 @@ void LayerTreeHostImpl::setNeedsRedraw()
 
 bool LayerTreeHostImpl::ensureRenderSurfaceLayerList()
 {
-    activeTree()->UpdateDrawProperties();
+    activeTree()->UpdateDrawProperties(LayerTreeImpl::UPDATE_ACTIVE_TREE);
     return activeTree()->RenderSurfaceLayerList().size();
 }