Revert of remvoe duplicate impl for SkImageInfo flattening

src/gpu/GrSurface.cpp

Index: src/gpu/GrSurface.cpp
diff --git a/src/gpu/GrSurface.cpp b/src/gpu/GrSurface.cpp
index 1fcc4ff18be23eeb51dc843489a32c00dfbbf685..fed95f232fe4b18d34ef4f6d7844346aacc44eba 100644
--- a/src/gpu/GrSurface.cpp
+++ b/src/gpu/GrSurface.cpp
@@ -8,18 +8,8 @@
 #include "GrSurface.h"
 
 #include "SkBitmap.h"
-#include "SkGr.h"
 #include "SkImageEncoder.h"
 #include <stdio.h>
-
-void GrSurface::asImageInfo(SkImageInfo* info) const {
-    if (!GrPixelConfig2ColorType(this->config(), &info->fColorType)) {
-        sk_throw();
-    }
-    info->fWidth = this->width();
-    info->fHeight = this->height();
-    info->fAlphaType = kPremul_SkAlphaType;
-}
 
 bool GrSurface::savePixels(const char* filename) {
     SkBitmap bm;