Internalize JSON chunk merging to trace_event.h API (retry).

Original review: http://codereview.chromium.org/8355024/

BUG=100291
TEST=base_unittests, content_unittests

Review URL: http://codereview.chromium.org/8373018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@106924 0039d316-1c4b-4281-b951-d872f2087c98
11 files changed