Remove GrGpu.h from GrResourceProvider.h

Noticed this while cleaning up GrResourceProvider.h's usage. It seems like a powerful header to just be splashing around.

Change-Id: I686fea61354a7e3c1c759627ffe4a560f7945f83
Reviewed-on: https://skia-review.googlesource.com/20040
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/tests/ProxyRefTest.cpp b/tests/ProxyRefTest.cpp
index 61e5720..04510b3 100644
--- a/tests/ProxyRefTest.cpp
+++ b/tests/ProxyRefTest.cpp
@@ -11,6 +11,7 @@
 
 #if SK_SUPPORT_GPU
 #include "GrContextPriv.h"
+#include "GrGpuResourceRef.h"
 #include "GrRenderTargetProxy.h"
 #include "GrResourceProvider.h"
 #include "GrSurfaceProxy.h"