Remove devtools_instrumentation::kRasterTask in favor of frame viewer's one

Remove devtools_instrumentation::kRasterTask in favor of frame viewer's one

This removes RasterTask emitted through devtools instrumentation and adds
disabled-by-default-devtools.timeline to categories emitted with
frame_viewer_instrumentation classes (frame viewer's event has more details).

BUG=

Committed: https://crrev.com/cb0da5a15865b158e35c8ac9530355cd71d1e5dd
Cr-Commit-Position: refs/heads/master@{#308573}

[caseq, 2014-12-08 15:43:40]

caseq@chromium.org changed reviewers:
+ danakj@chromium.org, enne@chromium.org

[caseq, 2014-12-08 15:43:40]

Looks like we don't need both frame viewer's and devtools events and the former
has more details. Adding devtools category to all frame viewer events will
result in sending AnalyzeTask events to devtools, but
https://codereview.chromium.org/781583003/ takes care of this.

[danakj, 2014-12-08 16:22:24]

LGTM

[danakj, 2014-12-08 16:22:27]

The CQ bit was checked by danakj@chromium.org

[commit-bot: I haz the power, 2014-12-08 16:23:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/785913003/1

[commit-bot: I haz the power, 2014-12-08 17:18:03]

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

[commit-bot: I haz the power, 2014-12-08 17:18:04]

Try jobs failed on following builders:
  linux_chromium_rel_ng on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[caseq, 2014-12-16 12:58:29]

The CQ bit was checked by caseq@chromium.org

[commit-bot: I haz the power, 2014-12-16 12:59:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/785913003/1

[commit-bot: I haz the power, 2014-12-16 12:59:54]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-16 13:00:31]

Patchset 1 (id:??) landed as
https://crrev.com/cb0da5a15865b158e35c8ac9530355cd71d1e5dd
Cr-Commit-Position: refs/heads/master@{#308573}