Make SkGr.h private and remove unused functions

BUG=skia:

Change-Id: I6699d00c5412ed9d9bf14b032a08b06b1c766bce
Reviewed-on: https://skia-review.googlesource.com/9398
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 68a11bf..fc1c23a 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -45,7 +45,7 @@
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
 #include "GrRenderTarget.h"
-#include "SkGrPriv.h"
+#include "SkGr.h"
 
 #endif
 #include "SkClipOpPriv.h"