Bug 935380 - Part 1: Remove INIT_MODE_COPY since it was invalid for callers to use it. r=nrc
Bug 935380 - Part 2: Pass the actual rect that the RenderTarget represents as the first parameter to CreateRenderTarget. r=nrc
Bug 935380 - Part 3: Make CompositingRenderTarget store it's origin. r=nrc
Bug 935380 - Part 4: Make the Compositors use the RenderTarget's origin instead of aOffset. r=nrc
Bug 35380 - Part 5: Remove aOffset from everywhere. r=nrc