Add an extension bubble explaining which extensions are in dev mode.

Add an extension bubble explaining which extensions are in dev mode. 

Note: This is a brand new changelist (the other one got corrupt somehow). Review happened here: https://codereview.chromium.org/95133002/

In order to accomplish this without too much code duplication I refactored the common code of the newly added SuspiciousExtension bubble into a base class ExtensionMessageBubbleController and a derived class (SuspiciousExtensionBubbleController) to accomodate a new type of bubble (DevModeBubbleController). I also generalized the BubbleView code to just display whatever the controller tells it (and removed mentions of SuspiciousExtensions from it). 

The new controller has an action button (Disable) so new functionality was added to accomodate. 

BUG=328441
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=240767

[Finnur, 2013-12-13 21:59:09]

Committed patchset #9 manually as r240767.

[tapted, 2013-12-15 22:54:03]

https://codereview.chromium.org/114153003/diff/140001/chrome/browser/extensio...
File chrome/browser/extensions/dev_mode_bubble_controller.cc (right):

https://codereview.chromium.org/114153003/diff/140001/chrome/browser/extensio...
chrome/browser/extensions/dev_mode_bubble_controller.cc:42:
service_(extensions::ExtensionSystem::Get(profile)->extension_service()),
Not sure if it applies to PrfoileKeyedAPIs.. but I know ProfileKeyedServices
can't do this: While the ExtensionSystem is a valid dependency and you can be
assured that it is not NULL, the Extension*Service* remains NULL until the
profile is fully loaded.

See https://codereview.chromium.org/77773002 for a way I encountered & fixed
this in some other code.

Context: http://crbug.com/328715

[Finnur, 2013-12-16 14:57:02]

https://codereview.chromium.org/114153003/diff/140001/chrome/browser/extensio...
File chrome/browser/extensions/dev_mode_bubble_controller.cc (right):

https://codereview.chromium.org/114153003/diff/140001/chrome/browser/extensio...
chrome/browser/extensions/dev_mode_bubble_controller.cc:42:
service_(extensions::ExtensionSystem::Get(profile)->extension_service()),
Great tip. Looking at the tip of tree code I don't see a codepath that leads to
a crash, but perhaps the bubble won't show in all cases. I need to refactor this
code a bit, which will hopefully take care of this, but I'll keep an eye out for
this in the meantime. Thank you.

[Finnur, 2013-12-16 15:26:42]

See also my comment on the bug you filed.