Reland 55888: Allow per-plugin content settings.

      Now with Fixed Unit Tests!

Run with --enable-resource-content-settings and --enable-click-to-play to enable.

TabSpecificContentSettings now keeps track of which resources were blocked. The content setting bubble displays those resource, and selecting the &quotallow radio buttons adds exceptions for these resources.

The infobar for non-sandboxed plug-ins now also shows a button to always allow the blocked plug-in on that site.

Screenshot of the plugin bubble: http://imgur.com/6npqv.png

Because we need to change the title and radio button labels depending on whether we track specific plug-ins, we copy them from the ContentSettingBubbleModel.

XIB changes: Add a text field for the blocked plug-ins to ContentBlockedPlugins.xib, hooked up to the |blockedResourcesField_| outlet.

BUG=39252,38432
TEST=HostContentSettingsMapTest.*,manual

Review URL: http://codereview.chromium.org/2873104

Review URL: http://codereview.chromium.org/3124018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@56687 0039d316-1c4b-4281-b951-d872f2087c98