Reland Extension Installed InfoBubble

Reland Extension Installed InfoBubble 

(fix mac build breakage)

This creates UI feedback upon successful installation of an extension. An InfoBubble is shown containing the install icon and some information about how to manage extensions. 

TEST=Install a packaged extension. Verify the InfoBubble is shown, with the install icon and some description. The InfoBubble should disappear when the bubble looses focus (click elsewhere). For a browserAction, the bubble should point to the browserAction icon. For a pageAction **that has a "default_icon" set in it's manifest (see the samples/subscribe_page_action in this CL)**, it should point to a temporarily shown pageAction icon that will be hidden when the bubble closes. Otherwise it should point to the wrench menu. 

BUG=21412
TBR=willchan

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=31365