cc: Allow 'overflow: hidden' layers to be scrolled again.

cc/layers/layer_impl.cc

 // Copyright 2012 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/layers/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/json/json_reader.h"
 #include "base/strings/stringprintf.h"
 #include "cc/animation/animation_registrar.h"
@@ skipping 340 matching lines @@
   DCHECK(layer_tree_impl()->IsActiveTree());
 
   if (sent_scroll_delta_ == sent_scroll_delta)
     return;
 
   sent_scroll_delta_ = sent_scroll_delta;
 }
 
 gfx::Vector2dF LayerImpl::ScrollBy(gfx::Vector2dF scroll) {
   DCHECK(scrollable());
-  gfx::Vector2dF scroll_hidden;
-  if (!user_scrollable_horizontal_) {
-    scroll_hidden.set_x(scroll.x());
-    scroll.set_x(0.f);
-  }
-  if (!user_scrollable_vertical_) {
-    scroll_hidden.set_y(scroll.y());
-    scroll.set_y(0.f);
-  }
-
   gfx::Vector2dF min_delta = -scroll_offset_;
   gfx::Vector2dF max_delta = max_scroll_offset_ - scroll_offset_;
   // Clamp new_delta so that position + delta stays within scroll bounds.
   gfx::Vector2dF new_delta = (ScrollDelta() + scroll);
   new_delta.SetToMax(min_delta);
   new_delta.SetToMin(max_delta);
   gfx::Vector2dF unscrolled =
-      ScrollDelta() + scroll + scroll_hidden - new_delta;
+      ScrollDelta() + scroll - new_delta;
   SetScrollDelta(new_delta);
   return unscrolled;
 }
 
 void LayerImpl::ApplySentScrollDeltasFromAbortedCommit() {
   // Pending tree never has sent scroll deltas
   DCHECK(layer_tree_impl()->IsActiveTree());
 
   // Apply sent scroll deltas to scroll position / scroll delta as if the
   // main thread had applied them and then committed those values.
@@ skipping 80 matching lines @@
     return InputHandler::ScrollIgnored;
   }
 
   if (max_scroll_offset_.x() <= 0 && max_scroll_offset_.y() <= 0) {
     TRACE_EVENT0("cc",
                  "LayerImpl::tryScroll: Ignored. Technically scrollable,"
                  " but has no affordance in either direction.");
     return InputHandler::ScrollIgnored;
   }
 
-  if (!user_scrollable_horizontal_ && !user_scrollable_vertical_) {
-    TRACE_EVENT0("cc",
-                 "LayerImpl::TryScroll: Ignored. User gesture is not allowed"
-                 " to scroll this layer.");
-    return InputHandler::ScrollIgnored;
-  }
-
   return InputHandler::ScrollStarted;
 }
 
 bool LayerImpl::DrawCheckerboardForMissingTiles() const {
   return draw_checkerboard_for_missing_tiles_ &&
       !layer_tree_impl()->settings().background_color_instead_of_checkerboard;
 }
 
 gfx::Rect LayerImpl::LayerRectToContentRect(
     const gfx::RectF& layer_rect) const {
@@ skipping 917 matching lines @@
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue());
   AsValueInto(state.get());
   return state.PassAs<base::Value>();
 }
 
 void LayerImpl::RunMicroBenchmark(MicroBenchmarkImpl* benchmark) {
   benchmark->RunOnLayer(this);
 }
 
 }  // namespace cc