Moving GraphicsContext and dependencies from core to platform.

Source/platform/scroll/ScrollbarThemeMock.h

Index: Source/platform/scroll/ScrollbarThemeMock.h
diff --git a/Source/core/platform/mock/ScrollbarThemeMock.h b/Source/platform/scroll/ScrollbarThemeMock.h
similarity index 95%
rename from Source/core/platform/mock/ScrollbarThemeMock.h
rename to Source/platform/scroll/ScrollbarThemeMock.h
index 3ddf0268b78591265b82467af971524eb75dcc24..4011d40f7ce1174481fff0c9c55c2d7ee294315c 100644
--- a/Source/core/platform/mock/ScrollbarThemeMock.h
+++ b/Source/platform/scroll/ScrollbarThemeMock.h
@@ -26,12 +26,12 @@
 #ifndef ScrollbarThemeMock_h
 #define ScrollbarThemeMock_h
 
-#include "core/platform/ScrollbarTheme.h"
+#include "platform/scroll/ScrollbarTheme.h"
 
 namespace WebCore {
 
 // Scrollbar theme used in image snapshots, to eliminate appearance differences between platforms.
-class ScrollbarThemeMock : public ScrollbarTheme {
+class PLATFORM_EXPORT ScrollbarThemeMock : public ScrollbarTheme {
 public:
     virtual int scrollbarThickness(ScrollbarControlSize = RegularScrollbar) OVERRIDE;
     virtual bool usesOverlayScrollbars() const OVERRIDE;