Add record-as-much-as-possible mode for about://tracing.

Add record-as-much-as-possible mode for about://tracing.

Update DEPS for trace-viewer to include the 3 tracing modes selector.

BUG=396081
TEST=

Committed: https://crrev.com/8e752353b04c52cb3ba1d54b79fce241c0be53d3
Cr-Commit-Position: refs/heads/master@{#322689}

[nednguyen, 2015-03-27 21:53:39]

nednguyen@google.com changed reviewers:
+ nduca@chromium.org

[Nat, 2015-03-27 21:54:37]

nduca@google.com changed reviewers:
+ nduca@google.com

[Nat, 2015-03-27 21:54:37]

lgtm

[nednguyen, 2015-03-27 21:55:24]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2015-03-27 21:55:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1033223008/1

[commit-bot: I haz the power, 2015-03-27 22:05:47]

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

[commit-bot: I haz the power, 2015-03-27 22:05:48]

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...)

[nduca, 2015-03-27 22:21:58]

lgtm

[nednguyen, 2015-03-27 22:53:26]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2015-03-27 22:53:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1033223008/1

[commit-bot: I haz the power, 2015-03-28 00:47:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-28 00:47:55]

Patchset 1 (id:??) landed as
https://crrev.com/8e752353b04c52cb3ba1d54b79fce241c0be53d3
Cr-Commit-Position: refs/heads/master@{#322689}

[nednguyen, 2015-03-30 18:59:57]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1043973003/ by nednguyen@google.com.

The reason for reverting is: Speculative revert to see if this cause 340kb
increase in size (BUG=471610).