Make IsSolidColor() a property on CC scrollbar layers.

cc/animation/scrollbar_animation_controller_linear_fade_unittest.cc

Index: cc/animation/scrollbar_animation_controller_linear_fade_unittest.cc
diff --git a/cc/animation/scrollbar_animation_controller_linear_fade_unittest.cc b/cc/animation/scrollbar_animation_controller_linear_fade_unittest.cc
index e4aef862b2117f833d1c07b7fb7dc0c5a130e8a1..a854b8f7c7f1fae1bfd022d27e5f6f7d402220af 100644
--- a/cc/animation/scrollbar_animation_controller_linear_fade_unittest.cc
+++ b/cc/animation/scrollbar_animation_controller_linear_fade_unittest.cc
@@ -21,7 +21,7 @@ class ScrollbarAnimationControllerLinearFadeTest : public testing::Test {
   virtual void SetUp() {
     scroll_layer_ = LayerImpl::Create(host_impl_.active_tree(), 1);
     scrollbar_layer_ = ScrollbarLayerImpl::Create(
-        host_impl_.active_tree(), 2, HORIZONTAL);
+        host_impl_.active_tree(), 2, HORIZONTAL, false);
 
     scroll_layer_->SetMaxScrollOffset(gfx::Vector2d(50, 50));
     scroll_layer_->SetBounds(gfx::Size(50, 50));