Add an API to report debugName in GraphicsLayer

Source/core/platform/graphics/GraphicsLayerClient.h

Index: Source/core/platform/graphics/GraphicsLayerClient.h
diff --git a/Source/core/platform/graphics/GraphicsLayerClient.h b/Source/core/platform/graphics/GraphicsLayerClient.h
index 662ec203bedc8793b58c8f22702b06097272b795..62e4fe3072805f0111590257e312d37fcac3e20f 100644
--- a/Source/core/platform/graphics/GraphicsLayerClient.h
+++ b/Source/core/platform/graphics/GraphicsLayerClient.h
@@ -26,6 +26,8 @@
 #ifndef GraphicsLayerClient_h
 #define GraphicsLayerClient_h
 
+#include "wtf/text/WTFString.h"
+
 namespace WebCore {
 
 class FloatPoint;
@@ -77,6 +79,8 @@ public:
 
     virtual bool isTrackingRepaints() const { return false; }
 
+    virtual String debugName(const GraphicsLayer* graphicsLayer) { return String(); }
+
 #ifndef NDEBUG
     // RenderLayerBacking overrides this to verify that it is not
     // currently painting contents. An ASSERT fails, if it is.