add rowbytes option to allocPixels

TBR=

Author: reed@google.com

Review URL: https://codereview.chromium.org/345263005
diff --git a/src/lazy/SkCachingPixelRef.cpp b/src/lazy/SkCachingPixelRef.cpp
index 76510f6..97503e5 100644
--- a/src/lazy/SkCachingPixelRef.cpp
+++ b/src/lazy/SkCachingPixelRef.cpp
@@ -54,7 +54,7 @@
                                                      &bitmap);
     if (NULL == fScaledCacheId) {
         // Cache has been purged, must re-decode.
-        if ((!bitmap.setInfo(info, fRowBytes)) || !bitmap.allocPixels()) {
+        if (!bitmap.allocPixels(info, fRowBytes)) {
             fErrorInDecoding = true;
             return false;
         }