Remove ContextLifecycleObserver from SpeechSynthesisUtterance

Remove ContextLifecycleObserver from SpeechSynthesisUtterance

SpeechSynthesisUtterance inherits from ContextLifecycleObserver just to
implement EventTarget::getExecutionContext(). Instead, SpeechSynthesisUtterance
should just hold a strong member to ExecutionContext.

BUG=610176
Committed: https://crrev.com/5b8e71f5097eccbf0e60e2b7d6c5ca9461c77de3
Cr-Commit-Position: refs/heads/master@{#436947}

[haraken, 2016-12-07 12:03:12]

haraken@chromium.org changed reviewers:
+ sigbjornf@opera.com

[haraken, 2016-12-07 12:03:12]

PTAL

[sof, 2016-12-07 12:05:47]

lgtm

[haraken, 2016-12-07 12:12:16]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2016-12-07 12:12:31]

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, 2016-12-07 14:38:02]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1481112736854590,
"parent_rev": "f392fec8c5bc476c8c26312c8e0bbada4a7bb6f7", "commit_rev":
"7646acd51017a8040a3af3699e78c2a133561bf0"}

[commit-bot: I haz the power, 2016-12-07 14:38:29]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-12-07 14:40:49]

Description was changed from

==========
Remove ContextLifecycleObserver from SpeechSynthesisUtterance

SpeechSynthesisUtterance inherits from ContextLifecycleObserver just to
implement EventTarget::getExecutionContext(). Instead, SpeechSynthesisUtterance
should just hold a strong member to ExecutionContext.

BUG=610176
==========

to

==========
Remove ContextLifecycleObserver from SpeechSynthesisUtterance

SpeechSynthesisUtterance inherits from ContextLifecycleObserver just to
implement EventTarget::getExecutionContext(). Instead, SpeechSynthesisUtterance
should just hold a strong member to ExecutionContext.

BUG=610176

Committed: https://crrev.com/5b8e71f5097eccbf0e60e2b7d6c5ca9461c77de3
Cr-Commit-Position: refs/heads/master@{#436947}
==========

[commit-bot: I haz the power, 2016-12-07 14:40:50]

Patchset 2 (id:??) landed as
https://crrev.com/5b8e71f5097eccbf0e60e2b7d6c5ca9461c77de3
Cr-Commit-Position: refs/heads/master@{#436947}