[Extensions UI] Have the ExtensionMessageBubble linked to a browser
Right now, the ExtensionMessageBubbleController will try and
find the most recently used browser if it needs to open a link.
Instead, it should be linked to a particular browser, since it is
shown in a single browser. This also fixes a crash where it
was improperly using a developer tools window browser and
trying to navigate it.
BUG=515853
Review URL: https://codereview.chromium.org/
1265093007
Cr-Commit-Position: refs/heads/master@{#342156}