impl getROPixels for gpu SkImage

BUG=skia:
R=jvanverth@google.com

Review URL: https://codereview.chromium.org/150513005

git-svn-id: http://skia.googlecode.com/svn/trunk@13352 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/benchmain.cpp b/bench/benchmain.cpp
index 49ef00d..13241e9 100644
--- a/bench/benchmain.cpp
+++ b/bench/benchmain.cpp
@@ -154,7 +154,7 @@
     SkString path = SkOSPath::SkPathJoin(dir, filename.c_str());
     ::remove(path.c_str());
 
-    SkFILEWStream   stream(filename.c_str());
+    SkFILEWStream   stream(path.c_str());
     stream.write(data->data(), data->size());
 }