base: Factor task debug annotations out of MessageLoop

base: Factor task debug annotations out of MessageLoop

The MessageLoop has some code for adding debug annotations such as trace
flows and memory usage tags to posted tasks. Since we want to use these
annotations more generally for tasks that are scheduled outside the base
message loop, this patch factors it out into a standalone class.

TEST=TaskAnnotatorTest
BUG=391005
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=289560

[eseidel, 2014-08-12 16:18:50]

I haz no powers here, but I can poke brettw when I see him in mtv today.

https://codereview.chromium.org/455833004/diff/60001/base/message_loop/messag...
File base/message_loop/message_loop.h (right):

https://codereview.chromium.org/455833004/diff/60001/base/message_loop/messag...
base/message_loop/message_loop.h:432: debug::TaskAnnotator* task_annotator() {
return &task_annotator_; }
Does Chromium use 'const' here?

[Sami, 2014-08-12 16:58:00]

https://codereview.chromium.org/455833004/diff/60001/base/message_loop/messag...
File base/message_loop/message_loop.h (right):

https://codereview.chromium.org/455833004/diff/60001/base/message_loop/messag...
base/message_loop/message_loop.h:432: debug::TaskAnnotator* task_annotator() {
return &task_annotator_; }
On 2014/08/12 16:18:49, eseidel wrote:
> Does Chromium use 'const' here?

Making the method const would require a const_cast<> around the pointer. I did a
quick search and didn't find any accessors that do that.

[Sami, 2014-08-13 11:07:56]

brettw, ping?

[brettw, 2014-08-13 17:18:16]

lgtm

[Sami, 2014-08-13 17:21:16]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2014-08-13 17:22:25]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/skyostil@chromium.org/455833004/60001

[commit-bot: I haz the power, 2014-08-14 06:26:43]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_aosp on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_aosp/bu...)

[commit-bot: I haz the power, 2014-08-14 12:29:03]

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

[commit-bot: I haz the power, 2014-08-14 12:29:04]

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

[Sami, 2014-08-14 12:40:59]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2014-08-14 12:43:01]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/skyostil@chromium.org/455833004/60001

[commit-bot: I haz the power, 2014-08-14 14:26:24]

Committed patchset #4 (60001) as 289560