Error handling and refactoring in tools/linux/procfs.py, and rename multi-process-rss.py.

BUG=324194
TEST=None
NOTRY=True

Review URL: https://codereview.chromium.org/108073002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242476 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242476