Merge Compositor's ScrollbarAnimationControllers into single class

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 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 "content/renderer/gpu/render_widget_compositor.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 370 matching lines @@
 
   settings.using_synchronous_renderer_compositor = using_synchronous_compositor;
   if (using_synchronous_compositor) {
     // Android WebView uses system scrollbars, so make ours invisible.
     // http://crbug.com/677348: This can't be done using hide_scrollbars
     // setting because supporting -webkit custom scrollbars is still desired
     // on sublayers.
     settings.scrollbar_animator = cc::LayerTreeSettings::NO_ANIMATOR;
     settings.solid_color_scrollbar_color = SK_ColorTRANSPARENT;
   } else {
-    settings.scrollbar_animator = cc::LayerTreeSettings::LINEAR_FADE;
+    settings.scrollbar_animator = cc::LayerTreeSettings::ANDROID_OVERLAY;
     settings.scrollbar_fade_delay = base::TimeDelta::FromMilliseconds(300);
     settings.scrollbar_fade_resize_delay =
         base::TimeDelta::FromMilliseconds(2000);
     settings.scrollbar_fade_duration = base::TimeDelta::FromMilliseconds(300);
     settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
   }
   settings.renderer_settings.highp_threshold_min = 2048;
   // Android WebView handles root layer flings itself.
   settings.ignore_root_layer_flings = using_synchronous_compositor;
   // Memory policy on Android WebView does not depend on whether device is
@@ skipping 18 matching lines @@
   }
   // Webview does not own the surface so should not clear it.
   settings.renderer_settings.should_clear_root_render_pass =
       !using_synchronous_compositor;
 
   // TODO(danakj): Only do this on low end devices.
   settings.create_low_res_tiling = true;
 #else  // defined(OS_ANDROID)
 #if !defined(OS_MACOSX)
   if (ui::IsOverlayScrollbarEnabled()) {
-    settings.scrollbar_animator = cc::LayerTreeSettings::THINNING;
+    settings.scrollbar_animator = cc::LayerTreeSettings::AURA_OVERLAY;
     settings.scrollbar_fade_delay = ui::kOverlayScrollbarFadeOutDelay;
     settings.scrollbar_fade_resize_delay =
         ui::kOverlayScrollbarFadeOutDelay;
     settings.scrollbar_fade_duration =
         ui::kOverlayScrollbarFadeOutDuration;
     settings.scrollbar_thinning_duration =
         ui::kOverlayScrollbarThinningDuration;
   } else {
     // TODO(bokan): This section is probably unneeded? We don't use scrollbar
     // animations for non overlay scrollbars.
-    settings.scrollbar_animator = cc::LayerTreeSettings::LINEAR_FADE;
+    settings.scrollbar_animator = cc::LayerTreeSettings::ANDROID_OVERLAY;

[ncarter (slow), 2017/02/17 20:47:17]

As a result of the renaming, this looks weirder than before, because we're using
an ANDROID_ constant inside a !defined(OS_ANDROID) #ifdef context.

I don't particularly mind either style of name, but as someone who isn't
familiar with this code, I found it much easier to understand the original
THINNING/LINEAR_FADE names.

lgtm because I don't want to bikeshed, but maybe you could add comments to the
enum declarations like: // Android-style linear fade animation ?

[chaopeng, 2017/02/17 21:35:58]

We have a plan to fix Mac scrollbar and this TODO soon. 

[bokan, 2017/02/21 15:49:56]

This is already for non-Mac. I think we could just remove this section without
breaking anything. Could you put up a patch?

     settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
     settings.scrollbar_fade_delay = base::TimeDelta::FromMilliseconds(500);
     settings.scrollbar_fade_resize_delay =
         base::TimeDelta::FromMilliseconds(500);
     settings.scrollbar_fade_duration = base::TimeDelta::FromMilliseconds(300);
   }
 #endif  // !defined(OS_MACOSX)
 
   // On desktop, if there's over 4GB of memory on the machine, increase the
   // image decode budget to 256MB for both gpu and software.
@@ skipping 669 matching lines @@
 void RenderWidgetCompositor::SetDeviceColorSpace(
     const gfx::ColorSpace& color_space) {
   layer_tree_host_->SetDeviceColorSpace(color_space);
 }
 
 void RenderWidgetCompositor::SetIsForOopif(bool is_for_oopif) {
   is_for_oopif_ = is_for_oopif;
 }
 
 }  // namespace content