Replace getBaseLayerSize() with the size passed to DrawingRecorder.

third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 191 matching lines @@
     part = WebThemeEngine::kPartScrollbarVerticalThumb;
 
   blink::WebThemeEngine::ExtraParams params;
   params.scrollbar_thumb.scrollbar_theme =
       static_cast<WebScrollbarOverlayColorTheme>(
           scrollbar.GetScrollbarOverlayColorTheme());
 
   // Horizontally flip the canvas if it is left vertical scrollbar.
   if (scrollbar.IsLeftSideVerticalScrollbar()) {
     canvas->save();
-    canvas->translate(canvas->getBaseLayerSize().width(), 0);
+    canvas->translate(rect.Width(), 0);
     canvas->scale(-1, 1);
   }
 
   Platform::Current()->ThemeEngine()->Paint(canvas, part, state, WebRect(rect),
                                             &params);
 
-  if (scrollbar.IsLeftSideVerticalScrollbar())
+  if (scrollbar.IsLeftSideVerticalScrollbar()) {
+    canvas->clear(SK_ColorRED);

[danakj, 2017/04/18 19:27:12]

Oops bonus clear for testing.

     canvas->restore();
+  }
 }
 
 ScrollbarPart ScrollbarThemeOverlay::HitTest(
     const ScrollbarThemeClient& scrollbar,
     const IntPoint& position) {
   if (allow_hit_test_ == kDisallowHitTest)
     return kNoPart;
 
   ScrollbarPart part = ScrollbarTheme::HitTest(scrollbar, position);
   if (part != kThumbPart)
@@ skipping 59 matching lines @@
         .height;
   }
 
   return Platform::Current()
       ->ThemeEngine()
       ->GetSize(WebThemeEngine::kPartScrollbarHorizontalThumb)
       .width;
 }
 
 }  // namespace blink