Use stack allocation for Android data in SkScalerContext::MakeRec().

In a perfvis run on the "Boogie" test page, descriptorProc() during
detachCache() was taking .721 ms, and 20% of that was the flatten() in
MakeRec(). Changing this to a smaller stack allocation reduces the time
for descriptorProc() to .556 ms.

R=reed@google.com, bsalomon@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/372323003
1 file changed