cc: remove unused devtools_instrumentation events

As a follow-up to r238586 and blink r162771, remove devtools_instrumentation
constants that are no long used in cc and do not generate events that are
no longer processed by Timeline.

TBR=enne,danakj
BUG=322207

Review URL: https://codereview.chromium.org/103703003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238700 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238700