Save vector icons in a cache (a la ResourceBundle).

Save vector icons in a cache (a la ResourceBundle).

This means we only have to actually draw one time (per image/color/size)
and the bytes will be stored thereafter. The drawing is the most expensive
part so this should be a performance optimization. This also means we will
share memory between two places that use the same icon. However, this also
means that memory is never freed.

One other motivation for this change is that parts of Chrome's codebase
(in particular favicons) deal in raw pointers to png data, which it assumes
will last indefinitely.

BUG=505953
Committed: https://crrev.com/2ee31b326a16ab5bb18a89432a5e1c9a06363da3
Cr-Commit-Position: refs/heads/master@{#340902}

[Evan Stade, 2015-07-28 22:34:51]

estade@chromium.org changed reviewers:
+ sky@chromium.org

[Evan Stade, 2015-07-28 22:34:52]

estade@chromium.org changed reviewers:
+ sky@chromium.org

[sky, 2015-07-28 23:55:37]

LGTM

[Evan Stade, 2015-07-29 16:17:36]

The CQ bit was checked by estade@chromium.org

[commit-bot: I haz the power, 2015-07-29 16:17:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1266463002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1266463002/20001

[commit-bot: I haz the power, 2015-07-29 16:50:01]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-07-29 16:51:17]

Patchset 2 (id:??) landed as
https://crrev.com/2ee31b326a16ab5bb18a89432a5e1c9a06363da3
Cr-Commit-Position: refs/heads/master@{#340902}