Adding instrumentation to locate the source of jankiness.

Adding instrumentation to locate the source of jankiness.

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.
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=455884, 455942, 455952
TEST=none
TBR=mmenke,michaeln,zea

Committed: https://crrev.com/3b6d4f8fc68682ba786a1a0c8fcb6b7005d7e8cf
Cr-Commit-Position: refs/heads/master@{#314970}

[Peter Kasting, 2015-02-06 01:11:20]

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

[vadimt, 2015-02-06 01:48:09]

LGTM with an optional comment.

https://codereview.chromium.org/900793009/diff/1/content/browser/loader/resou...
File content/browser/loader/resource_dispatcher_host_impl.cc (right):

https://codereview.chromium.org/900793009/diff/1/content/browser/loader/resou...
content/browser/loader/resource_dispatcher_host_impl.cc:2173:
FROM_HERE_WITH_EXPLICIT_FUNCTION(
Will work, but you don't need curlies. The time in the nested instrumentation
(UpdateLoadStates3) will be subtracted anyways.

[Peter Kasting, 2015-02-06 01:54:54]

https://codereview.chromium.org/900793009/diff/1/content/browser/loader/resou...
File content/browser/loader/resource_dispatcher_host_impl.cc (right):

https://codereview.chromium.org/900793009/diff/1/content/browser/loader/resou...
content/browser/loader/resource_dispatcher_host_impl.cc:2173:
FROM_HERE_WITH_EXPLICIT_FUNCTION(
On 2015/02/06 01:48:08, vadimt wrote:
> Will work, but you don't need curlies. The time in the nested instrumentation
> (UpdateLoadStates3) will be subtracted anyways.

I didn't want the code at the bottom of the function included in the time for
either of these last two objects.

It's moot anyway, I'm changing how I instrument this based on comments in bug
455952.

[Peter Kasting, 2015-02-06 01:56:53]

New patchsets have been uploaded after l-g-t-m from vadimt@chromium.org

[vadimt, 2015-02-06 02:03:13]

OK, you are hereby granted the "instrumentation readability"; and there is no
need to send me further reviews, except the first one that uses
ScopedTracker::TrackCallback.
Please do several likewise first reviews for your jankiness group members.

Some additional wisdom:
1. Instrumenting loops can hide jank and in extreme cases harm perf
2. Never try to calculate the param to FROM_HERE_WITH_EXPLICIT_FUNCTION. It must
be a string constant.
3. Add curlies when instrumenting single-line 'ifs'. I'm not an idiot, but I
forgot one time, but was luckily caught by units.

[Peter Kasting, 2015-02-06 02:05:50]

pkasting@chromium.org changed reviewers:
+ michaeln@chromium.org, mmenke@chromium.org, zea@chromium.org

[Peter Kasting, 2015-02-06 02:06:46]

TBRing for mechanical changes:
mmenke: chrome/browser/net/, content/browser/loader/, net/ OWNERS
michaeln: content/browser/appcache/, content/browser/service_worker/ OWNERS
zea: google_apis/, jingle/ OWNERS

[Peter Kasting, 2015-02-06 02:07:20]

The CQ bit was checked by pkasting@chromium.org

[commit-bot: I haz the power, 2015-02-06 02:08:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/900793009/40001

[commit-bot: I haz the power, 2015-02-06 03:49:47]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-02-06 03:50:43]

Patchset 3 (id:??) landed as
https://crrev.com/3b6d4f8fc68682ba786a1a0c8fcb6b7005d7e8cf
Cr-Commit-Position: refs/heads/master@{#314970}