Moving GraphicsContext and dependencies from core to platform.

Source/platform/graphics/Canvas2DLayerManager.h

Index: Source/platform/graphics/Canvas2DLayerManager.h
diff --git a/Source/core/platform/graphics/Canvas2DLayerManager.h b/Source/platform/graphics/Canvas2DLayerManager.h
similarity index 94%
rename from Source/core/platform/graphics/Canvas2DLayerManager.h
rename to Source/platform/graphics/Canvas2DLayerManager.h
index 551bfa6c1f2c2621c621052e232946c6484aa567..e2c4e042e6585647ae81c5fed3f74b7b932e2d64 100644
--- a/Source/core/platform/graphics/Canvas2DLayerManager.h
+++ b/Source/platform/graphics/Canvas2DLayerManager.h
@@ -25,14 +25,14 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef Canvas2DLayerManager_h
 #define Canvas2DLayerManager_h
 
-#include "core/platform/graphics/Canvas2DLayerBridge.h"
+#include "platform/graphics/Canvas2DLayerBridge.h"
 #include "public/platform/WebThread.h"
 
 class Canvas2DLayerManagerTest;
 
 namespace WebCore {
 
-class Canvas2DLayerManager : public blink::WebThread::TaskObserver {
+class PLATFORM_EXPORT Canvas2DLayerManager : public blink::WebThread::TaskObserver {
 public:
     static Canvas2DLayerManager& get();
     void init(size_t maxBytesAllocated, size_t targetBytesAllocated);