DevTools: Make Android tabs unloaded from memory accessible via remote debugging protocol (re-land of step 3)

The previous attempt (https://chromiumcodereview.appspot.com/25627004) broke telemetry tests because ChromiumTestShell has no tab models so json/list always returned an empty list.

This patch adds the targets not associated with any tabs to the list.


BUG=272174

Review URL: https://codereview.chromium.org/37173002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230755 0039d316-1c4b-4281-b951-d872f2087c98
Fix for public account layout bug CL.

On #11 comment.

BUG=249449
NOTRY=true

Review URL: https://codereview.chromium.org/40483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230756 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230756