Replace getBaseLayerSize() with the size passed to DrawingRecorder.

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

Index: third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
index a8c226868f1d8ffb2bd2282ee5f13bfea8c86840..ecd8e22904ed55e4567750bd260159c89c4f97d3 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollbarThemeOverlay.cpp
@@ -209,15 +209,17 @@ void ScrollbarThemeOverlay::PaintThumb(GraphicsContext& context,
   // 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(