Remove unused assets, update old assets

Remove unused assets, update old assets

- about_sys changes copied from about:memory-internals
- .topbutton-bar .gear-button was not used anywhere (not to be confused with file manager's #gear-button)
- some files moved to shared location or moved from shared location to specific location

TBR=fukino@chromium.org
BUG=522168, 505953
Committed: https://crrev.com/f149d9533f0e62e0f01d663dcc87d59e80d97b0a
Cr-Commit-Position: refs/heads/master@{#344247}

[Evan Stade, 2015-08-18 23:02:35]

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

[oshima, 2015-08-19 00:43:01]

lgtm

[Evan Stade, 2015-08-19 06:20:38]

The CQ bit was checked by estade@chromium.org

[commit-bot: I haz the power, 2015-08-19 06:20:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1296373003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1296373003/1

[commit-bot: I haz the power, 2015-08-19 06:29:17]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-19 06:29:18]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[Evan Stade, 2015-08-19 16:18:24]

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

[Evan Stade, 2015-08-19 16:18:25]

TBR fukino@ for ui/file_manager/ (it's just a file move)

[Evan Stade, 2015-08-19 16:18:30]

The CQ bit was checked by estade@chromium.org

[commit-bot: I haz the power, 2015-08-19 16:18:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1296373003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1296373003/1

[commit-bot: I haz the power, 2015-08-19 16:23:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-19 16:23:57]

Patchset 1 (id:??) landed as
https://crrev.com/f149d9533f0e62e0f01d663dcc87d59e80d97b0a
Cr-Commit-Position: refs/heads/master@{#344247}