Use correct ScrollbarTheme to paintScrollCorner

third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp

Index: third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
index 960e797a567a0e278c8e0bfb066efd0e17373b59..6426723396324ac22260716b896c3a59ba1c52d5 100644
--- a/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/PaintLayerCompositor.cpp
@@ -69,6 +69,7 @@
 #include "platform/graphics/paint/TransformDisplayItem.h"
 #include "platform/instrumentation/tracing/TraceEvent.h"
 #include "platform/json/JSONValues.h"
+#include "platform/scroll/ScrollbarTheme.h"
 
 namespace blink {
 
@@ -935,8 +936,9 @@ void PaintLayerCompositor::paintContents(const GraphicsLayer* graphicsLayer,
   if (scrollbar) {
     paintScrollbar(graphicsLayer, scrollbar, builder.context(), interestRect);
   } else {
+    ScrollbarTheme& theme = scrollbarThemeOfScrollCorner();
     FramePainter(*m_layoutView.frameView())
-        .paintScrollCorner(builder.context(), interestRect);
+        .paintScrollCorner(builder.context(), theme, interestRect);
   }
 
   // Replay the painted scrollbar content with the GraphicsLayer backing as the
@@ -959,6 +961,17 @@ Scrollbar* PaintLayerCompositor::graphicsLayerToScrollbar(
   return nullptr;
 }
 
+ScrollbarTheme& PaintLayerCompositor::scrollbarThemeOfScrollCorner() const {

[bokan, 2017/03/13 13:52:09]

FramePainter keeps a reference to frameView itself so you shouldn't need to
determine and pass this in from PaintLayerCompositor. Just determine the theme
from the scrollbars inside FramePainter.

+  if (m_layoutView.frameView()->horizontalScrollbar())
+    return m_layoutView.frameView()->horizontalScrollbar()->theme();
+
+  if (m_layoutView.frameView()->verticalScrollbar())
+    return m_layoutView.frameView()->verticalScrollbar()->theme();
+
+  NOTREACHED();
+  return ScrollbarTheme::theme();
+}
+
 bool PaintLayerCompositor::supportsFixedRootBackgroundCompositing() const {
   if (Settings* settings = m_layoutView.document().settings())
     return settings->getPreferCompositingToLCDTextEnabled();