Cleanup namespace usage in platform/graphics/[filters/* to skia/*] and platform/graphics/[B-D]*

Source/platform/graphics/Canvas2DLayerManager.h

Index: Source/platform/graphics/Canvas2DLayerManager.h
diff --git a/Source/platform/graphics/Canvas2DLayerManager.h b/Source/platform/graphics/Canvas2DLayerManager.h
index dd79a5839aa12f3f39f1badc63f358d20b931909..1f1c8595435e5bed98c673ff0a259b20e19a6b48 100644
--- a/Source/platform/graphics/Canvas2DLayerManager.h
+++ b/Source/platform/graphics/Canvas2DLayerManager.h
@@ -32,7 +32,7 @@ class Canvas2DLayerManagerTest;
 
 namespace blink {
 
-class PLATFORM_EXPORT Canvas2DLayerManager : public blink::WebThread::TaskObserver {
+class PLATFORM_EXPORT Canvas2DLayerManager : public WebThread::TaskObserver {
 public:
     static Canvas2DLayerManager& get();
 
@@ -61,7 +61,7 @@ private:
     friend class ::Canvas2DLayerManagerTest; // for unit testing
 };
 
-}
+} // namespace blink
 
 #endif