Delete StyleSheetList and support code.

Delete StyleSheetList and support code.

We don't need this since we don't expose the list of sheets from Document
or ShadowRoot in Sky. After removing this code I also simplified the
system and deleted StyleSheetCandidate and DocumentStyleSheetCollector
which don't really do anything anymore.

Even if we do want to add back a list of sheets later it won't need code
because we don't have a concept of a remote sheet like <link rel> did,
and we don't have to deal with non-CSS sheets.

R=ojan@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/c177d41b3b416f03c404559d5abca2a6ade333ac

[esprehn, 2014-12-12 21:55:13]

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

[ojan, 2014-12-12 23:38:39]

lgtm

https://codereview.chromium.org/803673003/diff/1/sky/engine/core/dom/Document...
File sky/engine/core/dom/DocumentStyleSheetCollection.cpp (right):

https://codereview.chromium.org/803673003/diff/1/sky/engine/core/dom/Document...
sky/engine/core/dom/DocumentStyleSheetCollection.cpp:50: if
(!isHTMLStyleElement(*node))
Nit: This could be an assert.

https://codereview.chromium.org/803673003/diff/1/sky/engine/core/dom/ShadowTr...
File sky/engine/core/dom/ShadowTreeStyleSheetCollection.cpp (right):

https://codereview.chromium.org/803673003/diff/1/sky/engine/core/dom/ShadowTr...
sky/engine/core/dom/ShadowTreeStyleSheetCollection.cpp:50: if
(!isHTMLStyleElement(*node))
I guess the same applies here.

[esprehn, 2014-12-12 23:48:05]

Committed patchset #1 (id:1) manually as
c177d41b3b416f03c404559d5abca2a6ade333ac (presubmit successful).