Fix crash in the experimental app list StartPageView.

Fix crash in the experimental app list StartPageView.

This CL fixes a crash in the StartPageView that was happening because
an observer was not being cleaned up on destruction.

This CL also adds a profile change unit test which serves as a
regression test for this issue.

BUG=378572
TEST=Have experimental app list enabled and switch between signed in profiles repeatedly. There should be no crash.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=274162

[tapted, 2014-05-30 09:01:38]

lgtm with a TEST= line -- ~have two profiles, and switch.

https://codereview.chromium.org/305123002/diff/60001/ui/app_list/views/app_li...
File ui/app_list/views/app_list_view_unittest.cc (right):

https://codereview.chromium.org/305123002/diff/60001/ui/app_list/views/app_li...
ui/app_list/views/app_list_view_unittest.cc:319: AppListMainView* main_view =
view_->app_list_main_view();
nit: these 4 lines are probably redundant; being run in RunDisplayTest().

The pagination model checks are probably good to keep though, since it's used
later.

[calamity, 2014-05-30 09:08:40]

The CQ bit was checked by calamity@chromium.org

[commit-bot: I haz the power, 2014-05-30 09:10:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/calamity@chromium.org/305123002/80001

[commit-bot: I haz the power, 2014-05-30 12:44:07]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_chromium_gn_compile_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_chromium_gn_c...)
  android_dbg_triggered_tests on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered...)
  chromium_presubmit on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/chromium_presubmit/bu...)
  linux_chromium_chromeos_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_chrome...)
  linux_chromium_clang_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_clang_...)
  linux_chromium_gn_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_gn_rel...)
  linux_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_rel/bu...)

[commit-bot: I haz the power, 2014-05-30 12:46:26]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-05-30 12:46:27]

Try jobs failed on following builders:
  linux_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_rel/bu...)

[calamity, 2014-06-02 01:28:01]

The CQ bit was checked by calamity@chromium.org

[commit-bot: I haz the power, 2014-06-02 01:28:09]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/calamity@chromium.org/305123002/100001

[commit-bot: I haz the power, 2014-06-02 03:10:22]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  ios_dbg_simulator on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/ios_dbg_simulator/bui...)

[commit-bot: I haz the power, 2014-06-02 05:31:51]

Change committed as 274162