Make IsSolidColor() a property on CC scrollbar layers.

webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc

Index: webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
diff --git a/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc b/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
index a8080212beb7ba55e548044a884ba70ec6fa86ad..b255405ef24dd53abc79d60fbeccfb388f6c69fb 100644
--- a/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
+++ b/webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.cc
@@ -4,6 +4,7 @@
 
 #include "webkit/renderer/compositor_bindings/web_scrollbar_layer_impl.h"
 
+#include "cc/base/switches.h"
 #include "cc/layers/scrollbar_layer.h"
 #include "third_party/WebKit/public/platform/WebScrollbar.h"
 #include "webkit/renderer/compositor_bindings/scrollbar_impl.h"
@@ -13,15 +14,21 @@ using cc::ScrollbarLayer;
 
 namespace webkit {
 
+static bool ForceSolidColorScrollbars() {
+  return cc::switches::ForceSolidColorScrollbars();
+}
+
 WebScrollbarLayerImpl::WebScrollbarLayerImpl(
     WebKit::WebScrollbar* scrollbar,
     WebKit::WebScrollbarThemePainter painter,
     WebKit::WebScrollbarThemeGeometry* geometry)
-    : layer_(new WebLayerImpl(ScrollbarLayer::Create(
-          scoped_ptr<cc::Scrollbar>(new ScrollbarImpl(
-              make_scoped_ptr(scrollbar),
-              painter,
-              make_scoped_ptr(geometry))).Pass(), 0))) {}
+    : layer_(new WebLayerImpl(
+          ScrollbarLayer::Create(scoped_ptr<cc::Scrollbar>(new ScrollbarImpl(
+                                     make_scoped_ptr(scrollbar),
+                                     painter,
+                                     make_scoped_ptr(geometry))).Pass(),
+                                 0,
+                                 ForceSolidColorScrollbars()))) {}
 
 WebScrollbarLayerImpl::~WebScrollbarLayerImpl() {}