DevTools shows overlay scrollbar for enabled aura overlay scrollbar and mac

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 412 matching lines @@
 
   if (cmd.HasSwitch(cc::switches::kSlowDownRasterScaleFactor)) {
     const int kMinSlowDownScaleFactor = 0;
     const int kMaxSlowDownScaleFactor = INT_MAX;
     GetSwitchValueAsInt(
         cmd, cc::switches::kSlowDownRasterScaleFactor, kMinSlowDownScaleFactor,
         kMaxSlowDownScaleFactor,
         &settings.initial_debug_state.slow_down_raster_scale_factor);
   }
 
+  // This is default overlay scrollbar settings for Android and DevTools mobile
+  // emulator. Aura Overlay Scrollbar will override below.
+  settings.scrollbar_animator = cc::LayerTreeSettings::ANDROID_OVERLAY;
+  settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
+  settings.scrollbar_fade_delay = base::TimeDelta::FromMilliseconds(300);
+  settings.scrollbar_fade_duration = base::TimeDelta::FromMilliseconds(300);
+
 #if defined(OS_ANDROID)
   bool using_synchronous_compositor =
       GetContentClient()->UsingSynchronousCompositing();
 
   settings.use_stream_video_draw_quad = true;
   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::ANDROID_OVERLAY;
-    settings.scrollbar_fade_delay = base::TimeDelta::FromMilliseconds(300);
-    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
   // low end, so always use default policy.
   bool use_low_memory_policy =
       base::SysInfo::IsLowEndDevice() && !using_synchronous_compositor;
   if (use_low_memory_policy) {
     // On low-end we want to be very carefull about killing other
@@ skipping 19 matching lines @@
   if (base::SysInfo::IsLowEndDevice()) {
     // When running on a low end device, we limit cached bytes to 2MB.
     // This allows a typical page to fit its images in cache, but prevents
     // most long-term caching.
     settings.decoded_image_cache_budget_bytes = 2 * 1024 * 1024;
   }
 
   // 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::AURA_OVERLAY;
     settings.scrollbar_fade_delay = ui::kOverlayScrollbarFadeDelay;
     settings.scrollbar_fade_duration = ui::kOverlayScrollbarFadeDuration;
     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::ANDROID_OVERLAY;
-    settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
-    settings.scrollbar_fade_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.
   const int kImageDecodeMemoryThresholdMB = 4 * 1024;
   if (base::SysInfo::AmountOfPhysicalMemoryMB() >=
       kImageDecodeMemoryThresholdMB) {
     settings.decoded_image_cache_budget_bytes = 256 * 1024 * 1024;
     settings.decoded_image_working_set_budget_bytes = 256 * 1024 * 1024;
   } else {
     // These are the defaults, but recorded here as well.
@@ skipping 697 matching lines @@
     const cc::LocalSurfaceId& local_surface_id) {
   layer_tree_host_->SetLocalSurfaceId(local_surface_id);
 }
 
 void RenderWidgetCompositor::NotifySwapTime(ReportTimeCallback callback) {
   QueueSwapPromise(base::MakeUnique<ReportTimeSwapPromise>(
       std::move(callback), base::ThreadTaskRunnerHandle::Get()));
 }
 
 }  // namespace content