Remove tracking of pending sheets.

Remove tracking of pending sheets.

I was going to remove all this anyway since we don't need it in sky, all sheets
are local and there's no concept of a pending sheet now.

I also removed the dirty bit I added to StyleSheetCollection. The bit
is not correct and is preventing us from correctly processing sheets and
invalidating style. I'll add it back later when I understand how to add
the dirty bit correctly.

R=ojan@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/e4ab7d74cc99092af0696ff11166889f5032b5ea

[esprehn, 2015-01-13 02:10:35]

esprehn@chromium.org changed reviewers:
+ ojan@chromium.org

[ojan, 2015-01-13 02:14:13]

lgtm

[esprehn, 2015-01-13 02:15:27]

Committed patchset #1 (id:1) manually as
e4ab7d74cc99092af0696ff11166889f5032b5ea (presubmit successful).