Expose a way to set a view's base background color.

Source/core/page/FrameView.cpp

Index: Source/core/page/FrameView.cpp
diff --git a/Source/core/page/FrameView.cpp b/Source/core/page/FrameView.cpp
index 26badff745b01edc786294db90f39d5761b6e9c3..ad4d9f7efae7da761f8ee92444ca2e7714a9f8d1 100644
--- a/Source/core/page/FrameView.cpp
+++ b/Source/core/page/FrameView.cpp
@@ -2041,8 +2041,11 @@ void FrameView::setBaseBackgroundColor(const Color& backgroundColor)
     else
         m_baseBackgroundColor = backgroundColor;
 
-    if (renderView() && renderView()->layer()->backing())
-        renderView()->layer()->backing()->updateContentsOpaque();
+    if (RenderLayerBacking* backing = renderView() ? renderView()->layer()->backing() : 0) {
+        backing->updateContentsOpaque();
+        if (backing->graphicsLayer())
+            backing->graphicsLayer()->setNeedsDisplay();
+    }
     recalculateScrollbarOverlayStyle();
 }