Properly attach InfoBarContainer when it is swapped to a new WebContents

Properly attach InfoBarContainer when it is swapped to a new WebContents

* Moves the swapping of the InfoBarService from TabAndroid::SwapWebContents() to after TabAndroid::InitWebContents() is called from Tab.setContentViewCore().  This is necessary because InitWebContents attaches the InfoBarService to the WebContents; trying to swap before this point means that the InfoBarContainer will be observing nothing.

* Fixes the ChromeShellActivity/Tab to properly update the ContentViewCore when it is swapped.  This fixes the "Distill page" menu item.

* Adds a test to try to prevent this from happening in the future.

BUG=469026
TEST=InfoBarTest.testInfoBarContainerSwapsWebContents
TBR=newt
Review URL: https://codereview.chromium.org/1049383008

Cr-Commit-Position: refs/heads/master@{#326642}

Committed: https://chromium.googlesource.com/chromium/src/+/ffcc397d404ede173c2c93e4c2a2969459fe9558

[gone, 2015-04-24 00:37:37]

dfalcantara@chromium.org changed reviewers:
+ newt@chromium.org

[gone, 2015-04-24 00:39:13]

Committed patchset #1 (id:1) manually as
ffcc397d404ede173c2c93e4c2a2969459fe9558 (presubmit successful).