[not for review - epic CL] Adding Elastic+Momentum+Layered scrolling to views::ScrollView

ui/compositor/compositor.cc

 // Copyright (c) 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 "ui/compositor/compositor.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <deque>
@@ skipping 21 matching lines @@
 #include "cc/surfaces/surface_manager.h"
 #include "cc/trees/layer_tree_host_in_process.h"
 #include "cc/trees/layer_tree_settings.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/compositor/compositor_observer.h"
 #include "ui/compositor/compositor_switches.h"
 #include "ui/compositor/compositor_vsync_manager.h"
 #include "ui/compositor/dip_util.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animator_collection.h"
+#include "ui/compositor/overscroll/ui_scroll_input_manager.h"
 #include "ui/gl/gl_switches.h"
 
 namespace {
 
 const double kDefaultRefreshRate = 60.0;
 const double kTestRefreshRate = 200.0;
 
 }  // namespace
 
 namespace ui {
@@ skipping 37 matching lines @@
       compositor_lock_(NULL),
       layer_animator_collection_(this),
       weak_ptr_factory_(this) {
   context_factory->GetSurfaceManager()->RegisterFrameSinkId(frame_sink_id_);
   root_web_layer_ = cc::Layer::Create();
 
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
 
   cc::LayerTreeSettings settings;
 
+#if defined(OS_MACOSX)
+  settings.enable_elastic_overscroll = true;
+#endif
+
   // This will ensure PictureLayers always can have LCD text, to match the
   // previous behaviour with ContentLayers, where LCD-not-allowed notifications
   // were ignored.
   settings.layers_always_allowed_lcd_text = true;
   // Use occlusion to allow more overlapping windows to take less memory.
   settings.use_occlusion_for_tile_prioritization = true;
   settings.renderer_settings.refresh_rate =
       context_factory_->DoesCreateTestContexts() ? kTestRefreshRate
                                                  : kDefaultRefreshRate;
   settings.main_frame_before_activation_enabled = false;
@@ skipping 79 matching lines @@
   cc::LayerTreeHostInProcess::InitParams params;
   params.client = this;
   params.shared_bitmap_manager = context_factory_->GetSharedBitmapManager();
   params.gpu_memory_buffer_manager =
       context_factory_->GetGpuMemoryBufferManager();
   params.task_graph_runner = context_factory_->GetTaskGraphRunner();
   params.settings = &settings;
   params.main_task_runner = task_runner_;
   params.animation_host = cc::AnimationHost::CreateMainInstance();
   host_ = cc::LayerTreeHostInProcess::CreateSingleThreaded(this, &params);
+
+  // Tie composited scrolling with whether the platform wants elastic scrolling.
+  // TODO(tapted): Use composited scrolling on all platforms.
+  if (settings.enable_elastic_overscroll) {
+    scroll_input_manager_.reset(
+        new UIScrollInputManager(host_->GetInputHandler()));
+  }
+
   UMA_HISTOGRAM_TIMES("GPU.CreateBrowserCompositor",
                       base::TimeTicks::Now() - before_create);
 
   animation_timeline_ =
       cc::AnimationTimeline::Create(cc::AnimationIdProvider::NextTimelineId());
   host_->GetLayerTree()->animation_host()->AddAnimationTimeline(
       animation_timeline_.get());
 
   host_->GetLayerTree()->SetRootLayer(root_web_layer_);
   host_->SetFrameSinkId(frame_sink_id_);
@@ skipping 336 matching lines @@
                     observer_list_,
                     OnCompositingLockStateChanged(this));
 }
 
 void Compositor::CancelCompositorLock() {
   if (compositor_lock_)
     compositor_lock_->CancelLock();
 }
 
 }  // namespace ui