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/ReadWriteAlphaTest.cpp b/tests/ReadWriteAlphaTest.cpp
index 531159f..344400c 100644
--- a/tests/ReadWriteAlphaTest.cpp
+++ b/tests/ReadWriteAlphaTest.cpp
@@ -15,6 +15,7 @@
 #include "GrResourceProvider.h"
 #include "GrSurfaceContext.h"
 #include "GrSurfaceProxy.h"
+#include "GrTextureProxy.h"
 #include "SkCanvas.h"
 #include "SkSurface.h"