make GrPaint.h private -- IWYU

prerequisit: https://codereview.chromium.org/2743533002/

BUG=skia:

Change-Id: I8c2f34a6df165744ddeaeabb562cd6d6a9679b6a
Reviewed-on: https://skia-review.googlesource.com/9461
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 7ac5a93..57500cd 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -10,7 +10,6 @@
 
 #include "GrCaps.h"
 #include "GrColor.h"
-#include "GrPaint.h"
 #include "GrRenderTarget.h"
 #include "SkMatrix.h"
 #include "SkPathEffect.h"
@@ -34,13 +33,17 @@
 class GrResourceEntry;
 class GrResourceCache;
 class GrResourceProvider;
+class GrSamplerParams;
 class GrTextBlobCache;
 class GrTextContext;
-class GrSamplerParams;
+class GrTextureProxy;
 class GrVertexBuffer;
 class GrSwizzle;
 class SkTraceMemoryDump;
 
+class SkImage;
+class SkSurfaceProps;
+
 class SK_API GrContext : public SkRefCnt {
 public:
     /**