IPC fuzzer: play_testcase.py tweaks.
1. Add --gdb-browser to run the browser process inside gdb.
2. Any additional arguments after testcase are passed to chrome.
3. Re-runnable chrome command printout.

BUG=260848

Review URL: https://codereview.chromium.org/141483003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246034 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246034