Remove experimental code fro grouping notifications from the same source.

BUG=320827

Review URL: https://codereview.chromium.org/117513006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242998 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242998
Roll trace-viewer r1069:r1084

TBR=nduca
BUG=

Review URL: https://codereview.chromium.org/117513007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242999 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243000 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243000