Speculative revert to diagnose crash in chrome. Revert "Add SkCachedData and use it for SkMipMap"

This reverts commit 92561a0b99ad6c08ab7a11dd1872f028199392e9.

crasher in question:
https://code.google.com/p/chromium/issues/detail?id=420178

Review URL: https://codereview.chromium.org/617613003
14 files changed