Move nonscrollable axis gloweffect suppression to renderer.

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 2295 matching lines @@
       applied_delta = ScrollLayerWithLocalDelta(layer_impl, pending_delta);
     }
 
     const float kEpsilon = 0.1f;
     if (layer_impl == InnerViewportScrollLayer()) {
       unused_root_delta.Subtract(applied_delta);
       if (std::abs(unused_root_delta.x()) < kEpsilon)
         unused_root_delta.set_x(0.0f);
       if (std::abs(unused_root_delta.y()) < kEpsilon)
         unused_root_delta.set_y(0.0f);
+      // Disable overscroll on axes which is impossible to scroll.
+      if (settings_.report_overscroll_only_for_scrollable_axes) {
+        gfx::SizeF ceiled_viewport_size =

[jdduke (slow), 2014/04/10 14:16:02]

You shouldn't need to check both viewport size and the max scroll offset,
something like this should be sufficient:

if (active_tree_->TotalMaxScrollOffset().x() <= kEpsilon)
  unused_root_delta.set_x(0.0f):
if (active_tree_->TotalMaxScrollOffset().y() <= kEpsilon)
  unused_root_delta.set_y(0.0f):

+            gfx::ToCeiledSize(active_tree_->ScrollableViewportSize());
+        gfx::SizeF root_layer_size = active_tree_->ScrollableSize();
+        if (!(ceiled_viewport_size.width() < root_layer_size.width())) {
+          if (std::abs(InnerViewportScrollLayer()->MaxScrollOffset().x()) <= 0)

[aelias_OOO_until_Jul13, 2014/04/10 16:28:37]

Please also check OuterViewportScrollLayer as I mentioned earlier.  For context,
this is for when this approach launches in the future:
https://docs.google.com/a/chromium.org/document/d/1KewSqexq4Pd99RUFB-yVoUIJoc...

+            unused_root_delta.set_x(0.0f);
+        }
+        if (!(ceiled_viewport_size.height() < root_layer_size.height())) {
+          if (std::abs(InnerViewportScrollLayer()->MaxScrollOffset().y()) <= 0)
+            unused_root_delta.set_y(0.0f);
+        }
+      }
     }
 
     // If the layer wasn't able to move, try the next one in the hierarchy.
     bool did_move_layer_x = std::abs(applied_delta.x()) > kEpsilon;
     bool did_move_layer_y = std::abs(applied_delta.y()) > kEpsilon;
     did_scroll_x |= did_move_layer_x;
     did_scroll_y |= did_move_layer_y;
     if (!did_move_layer_x && !did_move_layer_y) {
       // Scrolls should always bubble between the outer and inner viewports
       if (should_bubble_scrolls_ || !did_lock_scrolling_layer_ ||
@@ skipping 741 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