Modify the format output when a DOM-object leak is detected

Modifies the output to the following style:
  #LEAK renderer pid PID (DETAIL_IN_JSON_FORMAT)

Now, this leaking output is not used anywhere, and this will 
be used by https://codereview.chromium.org/148153009/.

See also:
https://docs.google.com/a/chromium.org/document/d/1sFAsZxeISKnbGdXoLZlB2tDZ8pvO102ePFQx6TX4X14/edit

BUG=332630

Review URL: https://codereview.chromium.org/142043010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251310 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251310