fix orig_rect==NULL case

Change-Id: I3bb4fbebf59cba2a67681e74530fc0fe51f1958f
Merge "fix orig_rect==NULL case"
Add an interface abstraction to the WebP worker thread implementation

This allows custom implementations of threading mecanism.

Patch by Leonhard Gruenschloss.

Change-Id: Id8ea5917acd2f24fa8bce79748d1747de2751614