Take MT jank into account when animating the scroll offset on CC

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>
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   host_impl_->DidFinishImplFrame();
 
   LayerImpl* scrolling_layer = host_impl_->CurrentlyScrollingLayer();
   EXPECT_EQ(host_impl_->OuterViewportScrollLayer(), scrolling_layer);
 
   // Verify no jump.
   float y = scrolling_layer->CurrentScrollOffset().y();
   EXPECT_TRUE(y > 1 && y < 49);
 }
 
+TEST_F(LayerTreeHostImplTest, ScrollAnimatedWithDelay) {
+  const gfx::Size content_size(1000, 1000);
+  const gfx::Size viewport_size(50, 100);
+  CreateBasicVirtualViewportLayers(viewport_size, content_size);
+
+  DrawFrame();
+
+  base::TimeTicks start_time =
+      base::TimeTicks() + base::TimeDelta::FromMilliseconds(100);
+  BeginFrameArgs begin_frame_args =
+      CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE);
+
+  // Create animation with a 100ms delay.
+  EXPECT_EQ(InputHandler::SCROLL_ON_IMPL_THREAD,
+            host_impl_
+                ->ScrollAnimated(gfx::Point(), gfx::Vector2d(0, 100),
+                                 base::TimeDelta::FromMilliseconds(100))
+                .thread);
+  LayerImpl* scrolling_layer = host_impl_->CurrentlyScrollingLayer();
+  EXPECT_EQ(host_impl_->OuterViewportScrollLayer(), scrolling_layer);
+
+  // First tick, animation is started.
+  begin_frame_args.frame_time = start_time;
+  host_impl_->WillBeginImplFrame(begin_frame_args);
+  host_impl_->UpdateAnimationState(true);
+  EXPECT_EQ(gfx::ScrollOffset(), scrolling_layer->CurrentScrollOffset());
+  host_impl_->DidFinishImplFrame();
+
+  // Second tick after 50ms, animation should be half way done since
+  // the duration due to delay is 100ms.
+  begin_frame_args.frame_time =
+      start_time + base::TimeDelta::FromMilliseconds(50);
+  host_impl_->WillBeginImplFrame(begin_frame_args);
+  host_impl_->UpdateAnimationState(true);
+  EXPECT_EQ(50, scrolling_layer->CurrentScrollOffset().y());
+  host_impl_->DidFinishImplFrame();
+
+  // Update target.
+  EXPECT_EQ(InputHandler::SCROLL_ON_IMPL_THREAD,
+            host_impl_
+                ->ScrollAnimated(gfx::Point(), gfx::Vector2d(0, 100),
+                                 base::TimeDelta::FromMilliseconds(150))
+                .thread);
+
+  // Third tick after 100ms, should be at the target position since update
+  // target was called with a large value of jank.
+  begin_frame_args.frame_time =
+      start_time + base::TimeDelta::FromMilliseconds(100);
+  host_impl_->WillBeginImplFrame(begin_frame_args);
+  host_impl_->UpdateAnimationState(true);
+  EXPECT_EQ(200, scrolling_layer->CurrentScrollOffset().y());
+}
+
 // Test that a smooth scroll offset animation is aborted when followed by a
 // non-smooth scroll offset animation.
 TEST_F(LayerTreeHostImplTimelinesTest, ScrollAnimatedAborted) {
   const gfx::Size content_size(1000, 1000);
   const gfx::Size viewport_size(500, 500);
   CreateBasicVirtualViewportLayers(viewport_size, content_size);
 
   DrawFrame();
 
   base::TimeTicks start_time =
@@ skipping 1080 matching lines @@
   EXPECT_TRUE(host_impl_->use_gpu_rasterization());
 
   // Re-initialize with a software output surface.
   output_surface_ = FakeOutputSurface::CreateDelegatingSoftware();
   host_impl_->InitializeRenderer(output_surface_.get());
   EXPECT_FALSE(host_impl_->use_gpu_rasterization());
 }
 
 }  // namespace
 }  // namespace cc