Use Popen.communicate() to pass the symbol names to c++filt for demangling.

Passing symbol names via the command line parameters is tricky and requires additional escaping.
For example, it doesn't work with names starting with "-[".

BUG=none
R=timurrrr@chromium.org

Review URL: https://codereview.chromium.org/110443004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240277 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240277