Fix bounds clamping during composited smooth scroll.

cc/trees/layer_tree_host_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/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 10057 matching lines @@
   host_impl_->WillBeginImplFrame(begin_frame_args);
   host_impl_->Animate();
   host_impl_->UpdateAnimationState(true);
 
   EXPECT_VECTOR_EQ(gfx::ScrollOffset(0, 100),
                    scrolling_layer->CurrentScrollOffset());
   EXPECT_EQ(NULL, host_impl_->CurrentlyScrollingLayer());
   host_impl_->DidFinishImplFrame();
 }
 
+// Test that smooth scrolls clamp correctly when bounds change mid-animation.
+TEST_F(LayerTreeHostImplTimelinesTest, ScrollAnimatedChangingBounds) {
+  const gfx::Size old_content_size(1000, 1000);
+  const gfx::Size new_content_size(750, 750);
+  const gfx::Size viewport_size(500, 500);
+
+  LayerImpl* content_layer =
+      CreateBasicVirtualViewportLayers(viewport_size, old_content_size);
+  SetNeedsRebuildPropertyTrees();
+  DrawFrame();
+
+  base::TimeTicks start_time =
+      base::TimeTicks() + base::TimeDelta::FromMilliseconds(100);
+  BeginFrameArgs begin_frame_args =
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE);
+
+  host_impl_->ScrollAnimated(gfx::Point(), gfx::Vector2d(500, 500));
+  LayerImpl* scrolling_layer = host_impl_->CurrentlyScrollingLayer();
+
+  begin_frame_args.frame_time = start_time;
+  host_impl_->WillBeginImplFrame(begin_frame_args);
+  host_impl_->Animate();
+  host_impl_->UpdateAnimationState(true);
+  host_impl_->DidFinishImplFrame();
+
+  content_layer->SetBounds(new_content_size);
+  scrolling_layer->SetBounds(new_content_size);
+  SetNeedsRebuildPropertyTrees();
+  DrawFrame();
+
+  begin_frame_args.frame_time =
+      start_time + base::TimeDelta::FromMilliseconds(200);
+  host_impl_->WillBeginImplFrame(begin_frame_args);
+  host_impl_->Animate();
+  host_impl_->UpdateAnimationState(true);
+  host_impl_->DidFinishImplFrame();
+
+  EXPECT_EQ(gfx::ScrollOffset(250, 250),
+            scrolling_layer->CurrentScrollOffset());
+}
+
 TEST_F(LayerTreeHostImplTest, InvalidLayerNotAddedToRasterQueue) {
   host_impl_->CreatePendingTree();
 
   Region empty_invalidation;
   scoped_refptr<RasterSource> raster_source_with_tiles(
       FakeRasterSource::CreateFilled(gfx::Size(10, 10)));
 
   std::unique_ptr<FakePictureLayerImpl> layer =
       FakePictureLayerImpl::Create(host_impl_->pending_tree(), 11);
   layer->SetBounds(gfx::Size(10, 10));
@@ skipping 617 matching lines @@
 
   // Re-initialize with a software output surface.
   output_surface_ = FakeOutputSurface::CreateSoftware(
       base::WrapUnique(new SoftwareOutputDevice));
   host_impl_->InitializeRenderer(output_surface_.get());
   EXPECT_FALSE(host_impl_->use_gpu_rasterization());
 }
 
 }  // namespace
 }  // namespace cc