Fix double subtraction of sent_delta on sync tree activation.

cc/layers/layer_impl_unittest.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/layers/layer_impl.h"
 
 #include "cc/layers/painted_scrollbar_layer_impl.h"
 #include "cc/output/filter_operation.h"
 #include "cc/output/filter_operations.h"
 #include "cc/test/fake_impl_proxy.h"
@@ skipping 416 matching lines @@
     // offset plus 1 in each direction.
     host_impl_.active_tree()->root_layer()->SetBounds(gfx::Size(1, 1));
     gfx::Vector2d max_scroll_offset(51, 81);
     layer()->SetBounds(gfx::Size(max_scroll_offset.x(), max_scroll_offset.y()));
   }
 
   LayerImpl* layer() {
     return host_impl_.active_tree()->root_layer()->children()[0];
   }
 
+  LayerTreeHostImpl& host_impl() { return host_impl_; }
+
   LayerTreeImpl* tree() { return host_impl_.active_tree(); }
 
   LayerTreeSettings settings() {
     LayerTreeSettings settings;
     settings.use_pinch_virtual_viewport = true;
     return settings;
   }
 
  private:
   FakeImplProxy proxy_;
@@ skipping 221 matching lines @@
   gfx::Vector2dF scroll_delta(20.5f, 8.5f);
 
   layer()->set_user_scrollable_vertical(false);
   layer()->SetScrollOffset(scroll_offset);
   gfx::Vector2dF unscrolled = layer()->ScrollBy(scroll_delta);
 
   EXPECT_VECTOR_EQ(gfx::Vector2dF(0, 8.5f), unscrolled);
   EXPECT_VECTOR_EQ(gfx::Vector2dF(30.5f, 5), layer()->TotalScrollOffset());
 }
 
+TEST_F(LayerImplScrollTest, PushPropertiesToMirrorsTotalScrollOffset) {
+  gfx::ScrollOffset scroll_offset(10, 5);
+  gfx::Vector2dF scroll_delta(12, 18);
+
+  host_impl().CreatePendingTree();
+
+  layer()->SetScrollOffset(scroll_offset);
+  gfx::Vector2dF unscrolled = layer()->ScrollBy(scroll_delta);
+
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(0, 0), unscrolled);
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(22, 23), layer()->TotalScrollOffset());
+
+  layer()->SetSentScrollDelta(scroll_delta);
+
+  scoped_ptr<LayerImpl> pending_layer =
+      LayerImpl::Create(host_impl().sync_tree(), layer()->id());
+  pending_layer->SetScrollOffset(layer()->TotalScrollOffset());
+
+  pending_layer->PushPropertiesTo(layer());
+
+  EXPECT_VECTOR_EQ(gfx::Vector2dF(22, 23), layer()->TotalScrollOffset());
+  EXPECT_VECTOR_EQ(layer()->TotalScrollOffset(),
+                   pending_layer->TotalScrollOffset());
+}
+
 TEST_F(LayerImplScrollTest, SetNewScrollbarParameters) {
   gfx::ScrollOffset scroll_offset(10, 5);
   layer()->SetScrollOffset(scroll_offset);
 
   scoped_ptr<PaintedScrollbarLayerImpl> vertical_scrollbar(
       PaintedScrollbarLayerImpl::Create(tree(), 100, VERTICAL));
   vertical_scrollbar->SetScrollLayerAndClipLayerByIds(
       layer()->id(), tree()->root_layer()->id());
 
   int expected_vertical_maximum =
       layer()->bounds().height() - tree()->root_layer()->bounds().height();
   EXPECT_EQ(expected_vertical_maximum, vertical_scrollbar->maximum());
   EXPECT_EQ(scroll_offset.y(), vertical_scrollbar->current_pos());
 
   scoped_ptr<PaintedScrollbarLayerImpl> horizontal_scrollbar(
       PaintedScrollbarLayerImpl::Create(tree(), 101, HORIZONTAL));
   horizontal_scrollbar->SetScrollLayerAndClipLayerByIds(
       layer()->id(), tree()->root_layer()->id());
 
   int expected_horizontal_maximum =
       layer()->bounds().width() - tree()->root_layer()->bounds().width();
   EXPECT_EQ(expected_horizontal_maximum, horizontal_scrollbar->maximum());
   EXPECT_EQ(scroll_offset.x(), horizontal_scrollbar->current_pos());
 }
 
 }  // namespace
 }  // namespace cc