Remove third_party/jemalloc

We weren't using it, weren't updating it, and don't want to do the
maintenance to keep it building.

BUG=82385
TBR=cpu
NOTRY=true

Review URL: https://codereview.chromium.org/154543003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249025 0039d316-1c4b-4281-b951-d872f2087c98
[Hotword] Some small fixes to the hotword_private extension api.

BUG=325439, 289023

Review URL: https://codereview.chromium.org/154683002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249026 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249026