Add MakeEmpty to GrIRect16

The GrLayerCache will use this capability.

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

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/232563007

git-svn-id: http://skia.googlecode.com/svn/trunk@14136 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed