Clean up likely reference leak in Ganesh custom stages.

http://codereview.appspot.com/6286047/



git-svn-id: http://skia.googlecode.com/svn/trunk@4146 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/GrSamplerState.h b/include/gpu/GrSamplerState.h
index fb59111..f52775d 100644
--- a/include/gpu/GrSamplerState.h
+++ b/include/gpu/GrSamplerState.h
@@ -165,8 +165,9 @@
         this->reset(kDefault_WrapMode, kDefault_Filter, GrMatrix::I());
     }
 
-    void setCustomStage(GrCustomStage* stage) {
+    GrCustomStage* setCustomStage(GrCustomStage* stage) {
         GrSafeAssign(fCustomStage, stage);
+        return stage;
     }
     GrCustomStage* getCustomStage() const { return fCustomStage; }