Moving GraphicsContext and dependencies from core to platform.

Source/platform/graphics/GraphicsLayerClient.h

Index: Source/platform/graphics/GraphicsLayerClient.h
diff --git a/Source/core/platform/graphics/GraphicsLayerClient.h b/Source/platform/graphics/GraphicsLayerClient.h
similarity index 97%
rename from Source/core/platform/graphics/GraphicsLayerClient.h
rename to Source/platform/graphics/GraphicsLayerClient.h
index 4c10e48034f1c1f648f31714b9c4f223e28a9765..fa7cdbb2dee5e4ee105c1f719ab54490cf7f1893 100644
--- a/Source/core/platform/graphics/GraphicsLayerClient.h
+++ b/Source/platform/graphics/GraphicsLayerClient.h
@@ -26,6 +26,7 @@
 #ifndef GraphicsLayerClient_h
 #define GraphicsLayerClient_h
 
+#include "platform/PlatformExport.h"
 #include "wtf/text/WTFString.h"
 
 namespace WebCore {
@@ -58,7 +59,7 @@ enum {
 };
 typedef unsigned LayerTreeFlags;
 
-class GraphicsLayerClient {
+class PLATFORM_EXPORT GraphicsLayerClient {
 public:
     virtual ~GraphicsLayerClient() {}