Adding instrumentation to locate the source of jankiness.

Adding instrumentation to locate the source of jankiness.

Previous instrumentations showed that TemplateURLService::ChangeToLoadedState
alone is responsible for 2.74 janks per hour in UI thread in Win (8.15 on Mac). I need to instrument
the code inside it to find out which part causes jank.

This is a mechanical change that adds instrumentation required to locate the
source of jankiness (i.e. a long-running fragment of code executed as a part of
the task that causes jank) in the code. See the bug for details on what kind of
jank we are after.
A number of similar CLs were landed, and none of them caused issues. They've
helped to find and fix janky code. The code of the instrumentation is highly
optimized and is not expected to affect performance. The code simply creates a
diagnostic task which is identical to ones created by PostTask or IPC message
handlers.

BUG=422460
Committed: https://crrev.com/76e9fa8f84ecc98851451506072401be4f781c8f
Cr-Commit-Position: refs/heads/master@{#302147}

[vadimt, 2014-10-29 21:52:49]

vadimt@chromium.org changed reviewers:
+ pkasting@chromium.org

[vadimt, 2014-10-29 21:52:49]

pkasting@, please provide OWNER's approval.

[Peter Kasting, 2014-10-30 19:11:42]

LGTM

[vadimt, 2014-10-30 19:42:43]

The CQ bit was checked by vadimt@chromium.org

[commit-bot: I haz the power, 2014-10-30 19:44:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/684333002/20001

[commit-bot: I haz the power, 2014-10-30 20:26:21]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-10-30 20:27:01]

Patchset 2 (id:??) landed as
https://crrev.com/76e9fa8f84ecc98851451506072401be4f781c8f
Cr-Commit-Position: refs/heads/master@{#302147}