Instrumenting the code to check if jank was caused by first access to mmapped pointer.

Instrumenting the code to check if jank was caused by first access to mmapped pointer.

After the fix, jankiness disappeared from the task tracked by this bug.
Before the fix, jankiness of URLRequestSimpleJob::StartAsync was 18.1jph.

However, jankiness of URLRequest::Delegate::OnResponseStarted went up from 23.7 to 42 jph.
That task is tracked by another bug 423948.

This could mean the page fault exception that moved to another place.
I'm instrumenting the suspicious place mentioned in earlier conversations.

BUG=422489
Committed: https://crrev.com/522a6a68af27cc55510c9d27b3407ff49143b9e3
Cr-Commit-Position: refs/heads/master@{#305046}

[vadimt, 2014-11-20 16:41:29]

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

[vadimt, 2014-11-20 16:41:29]

mmenke@, please provide OWNER's approval

[mmenke, 2014-11-20 16:44:21]

On 2014/11/20 16:41:29, vadimt wrote:
> mmenke@, please provide OWNER's approval

You'll need to update your other CL, so this doesn't conflict with it.  Once
you've done that (Or closed the other CL for now, pending resolution), I'm happy
to sign off.

[vadimt, 2014-11-20 16:48:58]

Yes, I removed this file from the other CL.

[mmenke, 2014-11-20 16:49:31]

On 2014/11/20 16:48:58, vadimt wrote:
> Yes, I removed this file from the other CL.

Thanks!  LGTM

[vadimt, 2014-11-20 16:50:12]

The CQ bit was checked by vadimt@chromium.org

[commit-bot: I haz the power, 2014-11-20 16:51:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/746483002/1

[mmenke, 2014-11-20 16:57:07]

On 2014/11/20 16:51:37, I haz the power (commit-bot) wrote:
> CQ is trying da patch. Follow status at
>  https://chromium-cq-status.appspot.com/patch-status/746483002/1

Oh, and if this is the cause of jank, it should be very easy to just move this
onto another thread, particularly now as we're just copying from one ref-counted
buffer to another.

[commit-bot: I haz the power, 2014-11-20 18:41:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-20 18:42:33]

Patchset 1 (id:??) landed as
https://crrev.com/522a6a68af27cc55510c9d27b3407ff49143b9e3
Cr-Commit-Position: refs/heads/master@{#305046}