Fix ComponentLoader unit tests on cros_trunk

Fix ComponentLoader unit tests on cros_trunk

Some ComponentLoader unit_tests are crashing on official chromeos bot
in IsNormalSession() due to uninitialized user manager.
This is hit when loading quickoffice component extension, which is
guarded with #if defined(GOOGLE_CHROME_BUILD), thus it's seen only on
official builds.

This makes sure that UserManager is initialized before checking
if a user is logged in.

Example trace:
#0 0x00000b44302e base::debug::StackTrace::StackTrace()
#1 0x00000b442c6c base::debug::(anonymous namespace)::StackDumpSignalHandler()
#2 0x0000f776f410 ([vdso]+0x40f)
#3 0x00000d702745 user_manager::UserManager::Get()
#4 0x00000e4c4bec extensions::ComponentLoader::EnableFileSystemInGuestMode()
#5 0x00000e4c5811 extensions::ComponentLoader::AddDefaultComponentExtensionsWithBackgroundPages()
#6 0x00000e4c523e extensions::ComponentLoader::AddDefaultComponentExtensions()
#7 0x000008fa03ff extensions::ComponentLoaderTest_LoadAll_Test::TestBody()

BUG=None

Committed: https://crrev.com/ef80df98a25445af7929593e8ab156556165f68a
Cr-Commit-Position: refs/heads/master@{#313122}

[tbarzic, 2015-01-23 20:03:56]

tbarzic@chromium.org changed reviewers:
+ asargent@chromium.org, dpolukhin@chromium.org

[tbarzic, 2015-01-23 20:03:56]

Let me know if you'd prefer to add "&& user_manager::UserManager::Get()" here:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/ext...

btw. failing builder:
http://master.chrome.corp.google.com:8011/builders/cros%20trunk/builds/29261

[asargent_no_longer_on_chrome, 2015-01-23 23:23:09]

Yeah, I think a better fix is to just add the null user manager check to
IsNormalSession(). 

If for some reason that doesn't work, the only object I'd have to the code as
you have it in this CL is that component_loader.cc and
component_laoder_unittest.cc are both already a little difficult to understand
with all the various #ifdef's for chromeos, and I'd rather we refactor the code
to add explicit interfaces that can have different implementations on different
platforms.

[tbarzic, 2015-01-24 00:06:34]

OK, done with checking that user manager is initialized in IsNormalSession.

[asargent_no_longer_on_chrome, 2015-01-24 00:26:33]

lgtm

[Dmitry Polukhin, 2015-01-26 07:54:54]

LGTM

Alternative solution could be initializing user manager in these tests. But I'm
fine with current solution too.

[tbarzic, 2015-01-26 19:33:40]

On 2015/01/26 07:54:54, Dmitry Polukhin wrote:
> LGTM
> 
> Alternative solution could be initializing user manager in these tests. But
I'm
> fine with current solution too.

Yep, initializing user manager in these tests was my initial proposal, but
Antony preferred this approach :)

[tbarzic, 2015-01-26 19:33:45]

The CQ bit was checked by tbarzic@chromium.org

[commit-bot: I haz the power, 2015-01-26 19:34:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/874483005/20001

[commit-bot: I haz the power, 2015-01-26 20:36:38]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-01-26 20:37:32]

Patchset 2 (id:??) landed as
https://crrev.com/ef80df98a25445af7929593e8ab156556165f68a
Cr-Commit-Position: refs/heads/master@{#313122}