DocumentThreadableLoader: Add guards for sync notifyFinished() in setResource()

DocumentThreadableLoader: Add guards for sync notifyFinished() in setResource()

In loadRequest(), setResource() can call clear() synchronously:
  DocumentThreadableLoader::clear()
  DocumentThreadableLoader::handleError()
  Resource::didAddClient()
  RawResource::didAddClient()
and thus |m_client| can be null while resource() isn't null after setResource(),
causing crashes (Issue 595964).

This CL checks whether |*this| is destructed and
whether |m_client| is null after setResource().

BUG=595964
Review-Url: https://codereview.chromium.org/1902683002
Cr-Commit-Position: refs/heads/master@{#391001}
(cherry picked from commit 2571533bbb5b554ff47205c8ef1513ccc0817c3e)

Committed: https://chromium.googlesource.com/chromium/src/+/4bb31bcd811ff8a7a625f9505cc340d6d4b29bbe

[hiroshige, 2016-05-06 05:41:09]

Description was changed from

==========
DocumentThreadableLoader: Add guards for sync notifyFinished() in setResource()

In loadRequest(), setResource() can call clear() synchronously:
  DocumentThreadableLoader::clear()
  DocumentThreadableLoader::handleError()
  Resource::didAddClient()
  RawResource::didAddClient()
and thus |m_client| can be null while resource() isn't null after setResource(),
causing crashes (Issue 595964).

This CL checks whether |*this| is destructed and
whether |m_client| is null after setResource().

BUG=595964

Review-Url: https://codereview.chromium.org/1902683002
Cr-Commit-Position: refs/heads/master@{#391001}
(cherry picked from commit 2571533bbb5b554ff47205c8ef1513ccc0817c3e)
==========

to

==========
DocumentThreadableLoader: Add guards for sync notifyFinished() in setResource()

In loadRequest(), setResource() can call clear() synchronously:
  DocumentThreadableLoader::clear()
  DocumentThreadableLoader::handleError()
  Resource::didAddClient()
  RawResource::didAddClient()
and thus |m_client| can be null while resource() isn't null after setResource(),
causing crashes (Issue 595964).

This CL checks whether |*this| is destructed and
whether |m_client| is null after setResource().

BUG=595964

Review-Url: https://codereview.chromium.org/1902683002
Cr-Commit-Position: refs/heads/master@{#391001}
(cherry picked from commit 2571533bbb5b554ff47205c8ef1513ccc0817c3e)

Committed:
https://chromium.googlesource.com/chromium/src/+/4bb31bcd811ff8a7a625f9505cc3...
==========

[hiroshige, 2016-05-06 05:41:11]

Committed patchset #1 (id:1) manually as
4bb31bcd811ff8a7a625f9505cc340d6d4b29bbe.