Hide pinch viewport scrollbars when near minimum scale.

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 <limits>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 383 matching lines @@
   } else if (cmd->HasSwitch(cc::switches::kEnablePinchVirtualViewport)) {
     // use_pinch_zoom_scrollbars is only true on desktop when non-overlay
     // scrollbars are in use.
     settings.use_pinch_zoom_scrollbars = true;
     settings.scrollbar_animator = cc::LayerTreeSettings::LinearFade;
     settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
   }
   settings.scrollbar_fade_delay_ms = 500;
   settings.scrollbar_fade_resize_delay_ms = 500;
   settings.scrollbar_fade_duration_ms = 300;
+
+  // When pinching in, only show the pinch-viewport overlay scrollbars if the
+  // page scale is at least some threshold away from the minimum. i.e. don't
+  // show the pinch scrollbars when at minimum scale.
+  settings.scrollbar_show_scale_threshold = 1.05f;
 #endif
 
   if (cmd->HasSwitch(switches::kEnableLowResTiling))
     settings.create_low_res_tiling = true;
   if (cmd->HasSwitch(switches::kDisableLowResTiling))
     settings.create_low_res_tiling = false;
 
   scoped_refptr<base::SingleThreadTaskRunner> compositor_thread_task_runner =
       compositor_deps_->GetCompositorImplThreadTaskRunner();
   scoped_refptr<base::SingleThreadTaskRunner>
@@ skipping 456 matching lines @@
   widget_->OnSwapBuffersAborted();
 }
 
 void RenderWidgetCompositor::RateLimitSharedMainThreadContext() {
   cc::ContextProvider* provider =
       compositor_deps_->GetSharedMainThreadContextProvider();
   provider->ContextGL()->RateLimitOffscreenContextCHROMIUM();
 }
 
 }  // namespace content