Simplify the shutdown sequence of Oilpan's heap

Simplify the shutdown sequence of Oilpan's heap

The current shutdown sequence is more complicated than necessary
since it was implemented in days when it was not guaranteed that
the main thread is the last thread that gets detached.

Today the main thread joins all other threads before calling Heap::shutdown(),
so we can assume that the main thread is the last thread that gets detached.
This CL simplifies the shutdown sequence relying on the assumption.

BUG=

Committed: https://crrev.com/3ae8ad9e6ddbfe21e31d889d4ce622a3ab09929d
Cr-Commit-Position: refs/heads/master@{#379766}

[haraken, 2016-03-02 16:28:09]

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

[haraken, 2016-03-02 16:28:10]

PTAL

[sof, 2016-03-02 18:14:29]

(Release assert added in Heap.cpp is triggering.)

[haraken, 2016-03-08 05:58:38]

Now the tests pass. PTAL.

[sof, 2016-03-08 06:10:27]

lgtm

(pointer event breakage non-Oilpan, but unrelated.)

[haraken, 2016-03-08 06:10:50]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2016-03-08 06:11:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1754313002/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1754313002/60001

[commit-bot: I haz the power, 2016-03-08 06:18:36]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2016-03-08 06:19:49]

Description was changed from

==========
Simplify the shutdown sequence of Oilpan's heap

The current shutdown sequence is more complicated than necessary
since it was implemented in days when it was not guaranteed that
the main thread is the last thread that gets detached.

Today the main thread joins all other threads before calling Heap::shutdown(),
so we can assume that the main thread is the last thread that gets detached.
This CL simplifies the shutdown sequence relying on the assumption.

BUG=
==========

to

==========
Simplify the shutdown sequence of Oilpan's heap

The current shutdown sequence is more complicated than necessary
since it was implemented in days when it was not guaranteed that
the main thread is the last thread that gets detached.

Today the main thread joins all other threads before calling Heap::shutdown(),
so we can assume that the main thread is the last thread that gets detached.
This CL simplifies the shutdown sequence relying on the assumption.

BUG=

Committed: https://crrev.com/3ae8ad9e6ddbfe21e31d889d4ce622a3ab09929d
Cr-Commit-Position: refs/heads/master@{#379766}
==========

[commit-bot: I haz the power, 2016-03-08 06:19:50]

Patchset 4 (id:??) landed as
https://crrev.com/3ae8ad9e6ddbfe21e31d889d4ce622a3ab09929d
Cr-Commit-Position: refs/heads/master@{#379766}

[haraken, 2016-03-10 01:13:23]

A revert of this CL (patchset #4 id:60001) has been created in
https://codereview.chromium.org/1783673002/ by haraken@chromium.org.

The reason for reverting is: 
https://chromium.googlesource.com/chromium/src/+/5940f25b9d91258d698a5ce9f48e...
caused the following crash:

https://bugs.chromium.org/p/chromium/issues/detail?id=593092

This CL needs to be reverted to revert the above CL.
.