NaCl: Move definition of the "ppapihook" IRT interface to the Chromium repo

This uses the new IRT construction API.

This will allow references to PPAPI to be removed from src/untrusted/irt
in the NaCl repo.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3787
TEST=browser_tests

Review URL: https://codereview.chromium.org/171093002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252119 0039d316-1c4b-4281-b951-d872f2087c98
Describe the Net.QuicSession.PublicResetAddressMismatch histogram.

The histogram was added in https://codereview.chromium.org/159143007/.

R=jar@chromium.org,rch@chromium.org
BUG=none
TEST=none
NOTRY=true

Review URL: https://codereview.chromium.org/171453002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252120 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252119
UMA histrograms to track MW support

BUG=329265

Review URL: https://codereview.chromium.org/150573004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252121 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252121