Prefer to forward-declare GraphicsContext in headers.

Source/platform/mac/LocalCurrentGraphicsContext.h

Index: Source/platform/mac/LocalCurrentGraphicsContext.h
diff --git a/Source/platform/mac/LocalCurrentGraphicsContext.h b/Source/platform/mac/LocalCurrentGraphicsContext.h
index 95e5b46b7972d431fe8e53015e558adadf7b3bdf..c382b1651a346b7a71a8c7e55d799fecd5f514ad 100644
--- a/Source/platform/mac/LocalCurrentGraphicsContext.h
+++ b/Source/platform/mac/LocalCurrentGraphicsContext.h
@@ -17,15 +17,16 @@
  * Boston, MA 02110-1301, USA.
  */
 
-#include "platform/graphics/GraphicsContext.h"
-#include "wtf/Noncopyable.h"
-
+#include "platform/PlatformExport.h"
 #include "skia/ext/skia_utils_mac.h"
+#include "wtf/Noncopyable.h"
 
 OBJC_CLASS NSGraphicsContext;
 
 namespace WebCore {
 
+class GraphicsContext;
+
 // This class automatically saves and restores the current NSGraphicsContext for
 // functions which call out into AppKit and rely on the currentContext being set
 class PLATFORM_EXPORT LocalCurrentGraphicsContext {