Decouple profile data from its representation in the profiles panel's sidebar

Sidebar items now listen to the changes in profile header and update themselves as appropriate. WebInspector.ProfileTypeSidebarSection was introduced to encapsulate part of the sidebar tree corresponding to a single profile type.

BUG=None
R=alph@chromium.org

Review URL: https://codereview.chromium.org/145273027

git-svn-id: svn://svn.chromium.org/blink/trunk@166393 bbb929c8-8fbe-4397-9dbb-9b2b20218538