Sky shouldn't crash on device rotate

Sky shouldn't crash on device rotate

There were two problems (both fixed in this CL):

1) When we were resized by the view manager, we forgot to deflate by the
   device-pixel-ratio when converting to engine types. That caused use to
   allocate a backing texture that was 9x what we needed.

2) When the surfaces system returned textures to us for re-use, we'd put them
   into the cache even if they were the old size. That caused us to thrash the
   texture cache. In this CL, we make the size of the textures in the cache
   explicit.

R=eseidel@chromium.org
BUG=449001
Committed: https://chromium.googlesource.com/external/mojo/+/bbef272e3930b827b836dc3b03a903ecc3c0b20e

[eseidel, 2015-01-24 00:41:57]

lgtm

[abarth-chromium, 2015-01-24 05:20:22]

Committed patchset #1 (id:1) manually as
bbef272e3930b827b836dc3b03a903ecc3c0b20e (presubmit successful).