Remove unused parameters from filter_texture

Trivial cleanup.

Review URL: https://codereview.chromium.org/665863003
Fix clearing issue in render_pictures

This bug only crops up when using the "--writeWholeImage" option in tile mode

Review URL: https://codereview.chromium.org/664103003
Add clip to layer cache

This CL adds the clip region to the GPU layer hoisting image cache. It also switches back to the old caching behavior of using the entire CTM in the cache key rather then just the upper 2x2. This latter change is to focus more on hoisting rather then caching.

It also includes 2 smaller fixes:
a) layer's that have an image filter are no longer atlased (b.c. doing so complicates applying the image filter)

b) the result of clipping the layer's bounds to the current clip is used as the hoisted layer's size. This reduces the amount of pixels drawn to match a normal (non-hoisted) draw pass.

Review URL: https://codereview.chromium.org/640773004