This CL enables dmprof visualizer to fold open categories in its graph part.

With this CL, when a user closes an open node in the menu tree,
the graph draws the closed category's size as one area.



BUG=259206

Review URL: https://codereview.chromium.org/32413005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230370 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230370