Revert of Remove deprecated extension notifications from ProcessManager

Revert of Remove deprecated extension notifications from ProcessManager (https://codereview.chromium.org/397743005/)

Reason for revert:
Suspected for Invalid Write / Unadressable / Uninitialized errors in 
Linux Tests (valgrind)(3) via ProcessManagerTest.ProcessGrouping and others starting 
http://build.chromium.org/p/chromium.memory.fyi/builders/Linux%20Tests%20%28valgrind%29%283%29/builds/38965

Errors like

Invalid write of size 8
  ObserverListBase<autofill::PersonalDataManagerObserver>::AddObserver(autofill::PersonalDataManagerObserver*) (base/observer_list.h:162)
  autofill::PersonalDataManager::AddObserver(autofill::PersonalDataManagerObserver*) (components/autofill/core/browser/personal_data_manager.cc:225)
  ...
  extensions::ProcessManagerTest::ProcessManagerTest() (extensions/browser/process_manager_unittest.cc:39)

and a range of uninitialized reads/jumps.

Original issue's description:
> Remove deprecated extension notifications from ProcessManager and use ExtensionRegistry instead.
> 
> BUG=354046
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=284366

TBR=rdevlin.cronin@chromium.org,limasdf@gmail.com
NOTREECHECKS=true
NOTRY=true
BUG=354046
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=284387

[tapted, 2014-07-21 01:56:24]

Created Revert of Remove deprecated extension notifications from ProcessManager

[commit-bot: I haz the power, 2014-07-21 01:56:58]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/tapted@chromium.org/407883003/1

[commit-bot: I haz the power, 2014-07-21 01:57:46]

Change committed as 284387