Adding a way to disable SkOffsetImageFilter's optimized path in blink/chrome

BUG=
R=senorblanco@chromium.org, reed@google.com, sugoi@google.com

Author: sugoi@chromium.org

Review URL: https://codereview.chromium.org/54543005

git-svn-id: http://skia.googlecode.com/svn/trunk/src@12075 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/effects/SkOffsetImageFilter.cpp b/effects/SkOffsetImageFilter.cpp
index fc8e71c..ecaf5e6 100644
--- a/effects/SkOffsetImageFilter.cpp
+++ b/effects/SkOffsetImageFilter.cpp
@@ -19,7 +19,11 @@
                                         SkIPoint* loc) {
     SkImageFilter* input = getInput(0);
     SkBitmap src = source;
+#ifdef SK_DISABLE_OFFSETIMAGEFILTER_OPTIMIZATION
+    if (false) {
+#else
     if (!cropRectIsSet()) {
+#endif
         if (input && !input->filterImage(proxy, source, matrix, &src, loc)) {
             return false;
         }