cc: Be less aggressive about scheduling for scroll handlers

cc/trees/thread_proxy.cc

Index: cc/trees/thread_proxy.cc
diff --git a/cc/trees/thread_proxy.cc b/cc/trees/thread_proxy.cc
index 4a95140226db8fd2c72da44e632ebdd880bf1f5e..f05083b9b7f0ca38ef529d19efd3612aedadeaa7 100644
--- a/cc/trees/thread_proxy.cc
+++ b/cc/trees/thread_proxy.cc
@@ -1327,8 +1327,7 @@ void ThreadProxy::RenewTreePriority() {
   bool smoothness_takes_priority =
       impl().layer_tree_host_impl->pinch_gesture_active() ||
       impl().layer_tree_host_impl->page_scale_animation_active() ||
-      (impl().layer_tree_host_impl->IsCurrentlyScrolling() &&
-       !impl().layer_tree_host_impl->scroll_affects_scroll_handler());
+      impl().layer_tree_host_impl->IsCurrentlyScrolling();
 
   // Schedule expiration if smoothness currently takes priority.
   if (smoothness_takes_priority)
@@ -1355,8 +1354,14 @@ void ThreadProxy::RenewTreePriority() {
   }
 
   impl().layer_tree_host_impl->SetTreePriority(priority);
-  impl().scheduler->SetSmoothnessTakesPriority(priority ==
-                                               SMOOTHNESS_TAKES_PRIORITY);
+
+  // Only put the scheduler in prefer_smoothness_mode if we don't have a scroll
+  // listener. This gives the scroll listener a better chance of handling
+  // scroll updates within the same frame. The tree itself is still kept in
+  // prefer smoothness mode to allow checkerboarding.
+  impl().scheduler->SetSmoothnessTakesPriority(

[brianderson, 2014/09/03 20:01:57]

Should we rename the concept in the scheduler since it isn't exactly the same
thing anymore?

Or maybe add scroll_affects_scroll_handler to the scheduler, along side
smoothness_takes_priority?

+      priority == SMOOTHNESS_TAKES_PRIORITY &&
+      !impl().layer_tree_host_impl->scroll_affects_scroll_handler());
 
   // Notify the the client of this compositor via the output surface.
   // TODO(epenner): Route this to compositor-thread instead of output-surface