[telemetry] Make single-benchmark measurements protected and undiscoverable.

This will reduce the ambiguity/name collisions between benchmarks and measurements. Also some minor cleanups.


BUG=None.
TEST=None.

Review URL: https://codereview.chromium.org/23455049

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231981 0039d316-1c4b-4281-b951-d872f2087c98
Docserver: Display enum value descriptions in API docs.

This modifies the json schema to allow both primitive types and
dictionaries with properties "name" and optional "description" for enum
values.

BUG=310454

Review URL: https://codereview.chromium.org/39113003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231982 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231981
Add code for new invalidation local ack system

Commits classes that are part of the infrastructure of the new local
acknowledgement system for invalidations, which will be based on
WeakHandles to AckHandlers.

BUG=233437

Review URL: https://codereview.chromium.org/40303005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231983 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231983