fix warning from scalar --> int32 conversion

BUG=

Review URL: https://codereview.appspot.com/7065050

git-svn-id: http://skia.googlecode.com/svn/trunk@7061 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 5961aaf..4e9f837 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -341,7 +341,7 @@
 
         size_t stretchedRowBytes = rtDesc.fWidth * bpp;
 
-        GrTexture* texture = fGpu->createTexture(rtDesc, stretchedPixels.get(), stretchedRowBytes);
+        SkDEBUGCODE(GrTexture* texture = )fGpu->createTexture(rtDesc, stretchedPixels.get(), stretchedRowBytes);
         GrAssert(NULL != texture);
     }