extensions: Fix synchronization in ContentScriptApiTest.ContentScriptOtherExtensions

extensions: Fix synchronization in ContentScriptApiTest.ContentScriptOtherExtensions

The ContentScriptApiTest.ContentScriptOtherExtensions has the following
flow:

1. Register the inject.js content script to run at 'document_end'
   time.
2. Load iframe_content.{html,js} in an iframe.
3. On DOMContentLoaded, set a 10ms timer to report the iframe's contents
   to the test harness.
4. In 'inject.js', rewrite the page's content.
5. In the test harness, verify that the page reports the content mutated
   by inject.js.

The problem is that the timer registered in step 3 races with the
task[1] triggering the injection script since there's no explicit
synchronization between the two. Currently this works by accident, but
an upcoming change[2] in the Blink Scheduler will cause the test to
actually become flaky.

This change fixes the test by making the iframe report its contents
based on the load event rather than DOMContentLoaded. Since this is
guaranteed to happen after the injection has finished, there's no
possibility of out-of-order execution.

BUG=696001, 701223
[1] blink::FrameLoader::finishedParsing
    => extensions::ScriptInjection::InjectJs
       => blink::SuspendableScriptExecutor::create
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=701223#c4

Review-Url: https://codereview.chromium.org/2800103002
Cr-Commit-Position: refs/heads/master@{#463294}
Committed: https://chromium.googlesource.com/chromium/src/+/7d68ce72674bc9189bd8bcf305823d75c044489d

[Sami, 2017-04-07 16:42:36]

Description was changed from

==========
extensions: Fix synchronization in
ContentScriptApiTest.ContentScriptOtherExtensions

The ContentScriptApiTest.ContentScriptOtherExtensions has the following
flow:

1. Register the inject.js content script to run at 'document_end'
   time.
2. Load iframe_content.{html,js} in an iframe.
3. On DOMContentLoaded, set a 10ms timer to report the iframe's contents
   to the test harness.
4. In 'inject.js', rewrite the page's content.
5. In the test harness, verify that the page reports the content mutated
   by inject.js.

The problem is that the timer registered in step 3 races with the
task[1] triggering the injection script since there's no explicit
synchronization between the two. Currently this works by accident, but
an upcoming change[2] in the Blink Scheduler will cause the test to
actually become flaky.

This change fixes the test by making the iframe report its contents
based on the load event rather than DOMContentLoaded. Since this is
guaranteed to happen after the injection has finished, there's no
possibility of out-of-order execution.

BUG=696001,701223

[1] blink::FrameLoader::finishedParsing
    => extensions::ScriptInjection::InjectJs
       => blink::SuspendableScriptExecutor::create
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=701223#c4
==========

to

==========
extensions: Fix synchronization in
ContentScriptApiTest.ContentScriptOtherExtensions

The ContentScriptApiTest.ContentScriptOtherExtensions has the following
flow:

1. Register the inject.js content script to run at 'document_end'
   time.
2. Load iframe_content.{html,js} in an iframe.
3. On DOMContentLoaded, set a 10ms timer to report the iframe's contents
   to the test harness.
4. In 'inject.js', rewrite the page's content.
5. In the test harness, verify that the page reports the content mutated
   by inject.js.

The problem is that the timer registered in step 3 races with the
task[1] triggering the injection script since there's no explicit
synchronization between the two. Currently this works by accident, but
an upcoming change[2] in the Blink Scheduler will cause the test to
actually become flaky.

This change fixes the test by making the iframe report its contents
based on the load event rather than DOMContentLoaded. Since this is
guaranteed to happen after the injection has finished, there's no
possibility of out-of-order execution.

BUG=696001,701223

[1] blink::FrameLoader::finishedParsing
    => extensions::ScriptInjection::InjectJs
       => blink::SuspendableScriptExecutor::create
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=701223#c4
==========

[Sami, 2017-04-07 16:42:36]

skyostil@chromium.org changed reviewers:
+ finnur@chromium.org

[Sami, 2017-04-07 16:42:47]

PTAL

[Sami, 2017-04-07 16:43:20]

The CQ bit was checked by skyostil@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-04-07 16:43:49]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-07 17:31:39]

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

[commit-bot: I haz the power, 2017-04-07 17:31:39]

Dry run: Try jobs failed on following builders:
  linux_chromium_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[Sami, 2017-04-07 17:39:58]

The CQ bit was checked by skyostil@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-04-07 17:40:48]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-07 19:50:44]

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

[commit-bot: I haz the power, 2017-04-07 19:50:45]

Dry run: This issue passed the CQ dry run.

[Finnur, 2017-04-10 15:39:22]

LGTM.

[Sami, 2017-04-10 15:40:19]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2017-04-10 15:40:43]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-10 16:47:28]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1491838819956310,
"parent_rev": "34416a7e3c4764a5594dd31fb9ab0305caa46a62", "commit_rev":
"7d68ce72674bc9189bd8bcf305823d75c044489d"}

[commit-bot: I haz the power, 2017-04-10 16:48:18]

Description was changed from

==========
extensions: Fix synchronization in
ContentScriptApiTest.ContentScriptOtherExtensions

The ContentScriptApiTest.ContentScriptOtherExtensions has the following
flow:

1. Register the inject.js content script to run at 'document_end'
   time.
2. Load iframe_content.{html,js} in an iframe.
3. On DOMContentLoaded, set a 10ms timer to report the iframe's contents
   to the test harness.
4. In 'inject.js', rewrite the page's content.
5. In the test harness, verify that the page reports the content mutated
   by inject.js.

The problem is that the timer registered in step 3 races with the
task[1] triggering the injection script since there's no explicit
synchronization between the two. Currently this works by accident, but
an upcoming change[2] in the Blink Scheduler will cause the test to
actually become flaky.

This change fixes the test by making the iframe report its contents
based on the load event rather than DOMContentLoaded. Since this is
guaranteed to happen after the injection has finished, there's no
possibility of out-of-order execution.

BUG=696001,701223

[1] blink::FrameLoader::finishedParsing
    => extensions::ScriptInjection::InjectJs
       => blink::SuspendableScriptExecutor::create
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=701223#c4
==========

to

==========
extensions: Fix synchronization in
ContentScriptApiTest.ContentScriptOtherExtensions

The ContentScriptApiTest.ContentScriptOtherExtensions has the following
flow:

1. Register the inject.js content script to run at 'document_end'
   time.
2. Load iframe_content.{html,js} in an iframe.
3. On DOMContentLoaded, set a 10ms timer to report the iframe's contents
   to the test harness.
4. In 'inject.js', rewrite the page's content.
5. In the test harness, verify that the page reports the content mutated
   by inject.js.

The problem is that the timer registered in step 3 races with the
task[1] triggering the injection script since there's no explicit
synchronization between the two. Currently this works by accident, but
an upcoming change[2] in the Blink Scheduler will cause the test to
actually become flaky.

This change fixes the test by making the iframe report its contents
based on the load event rather than DOMContentLoaded. Since this is
guaranteed to happen after the injection has finished, there's no
possibility of out-of-order execution.

BUG=696001,701223

[1] blink::FrameLoader::finishedParsing
    => extensions::ScriptInjection::InjectJs
       => blink::SuspendableScriptExecutor::create
[2] https://bugs.chromium.org/p/chromium/issues/detail?id=701223#c4

Review-Url: https://codereview.chromium.org/2800103002
Cr-Commit-Position: refs/heads/master@{#463294}
Committed:
https://chromium.googlesource.com/chromium/src/+/7d68ce72674bc9189bd8bcf30582...
==========

[commit-bot: I haz the power, 2017-04-10 16:48:20]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/7d68ce72674bc9189bd8bcf30582...