DownloadTestObserver should know when the DownloadManager was shutdown

DownloadTestObserver should know when the DownloadManager was shutdown

DownloadTestObserver now uses ManagerGoingDown() interface to know
whether its manager was shutdown. This allows it to use a raw pointer
instead of a refptr.

By removing the refptr to DownloadManager, this commit will help the
change of DownloadManager to be owned by BrowserContext instead of a
refcounted object.

Previously we were piggybacking on the refptr to bind callbacks with
download manager. Now we use weak pointers to the DownloadTestObserver
object itself, and it'll guard whether the download manager was
shutdown or not.

This patch also removes some outdated commentary about "file select
dialog".

BUG=237871
TEST=content_unittests and browser_tests with filter for Download\*

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=201539

[cmarcelo, 2013-05-20 18:02:28]

phajdan.jr: could you take a look at this please?

Added benjhayden as reviewer too because this is very related to DownloadManager
change he reviewed in another patch.

benjhayden: this is only the change for DownloadTestObserver with the fixes for
the comments you posted in my other request
https://codereview.chromium.org/14593012/

[Paweł Hajdan Jr., 2013-05-21 18:02:19]

-me, +rdsmith

Looks fine to me at a glance, but I'd prefer Randy to take a look to see whether
it matches the intent of the TODO.

If you need my stamp, please let me know.

[Randy Smith (Not in Mondays), 2013-05-21 18:15:45]

I'm happy relying on Ben's review.  It LGTM from a cursory glance (but wait for
Ben's review).

[benjhayden, 2013-05-21 18:18:58]

one nit then LGTM.

https://codereview.chromium.org/15485002/diff/1/content/public/test/download_...
File content/public/test/download_test_observer.cc (right):

https://codereview.chromium.org/15485002/diff/1/content/public/test/download_...
content/public/test/download_test_observer.cc:97: ASSERT_TRUE(manager ==
download_manager_);
Please use CHECK_EQ instead.

[commit-bot: I haz the power, 2013-05-21 21:22:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/caio.de.oliveira.filho@intel.com/15485...

[Paweł Hajdan Jr., 2013-05-21 21:30:52]

LGTM

[commit-bot: I haz the power, 2013-05-22 15:48:25]

Change committed as 201539