Roll chromium_revision d3db2ff..375f736

Mainly to bring in https://codereview.chromium.org/636083002
updates to opus.

Relevant changes (https://chromium.googlesource.com/chromium/src/+/d3db2ff..375f736/DEPS)
* buildtools: 6bc51af..1ca1f25
* third_party/libsrtp: 98284c8..6446144
* tools/gyp: a61e860..b13d8f2
* tools/swarming_client: bcb3bc3..41036ec

Clang version was not updated in this roll.

BUG=
R=marpan@google.com

Review URL: https://webrtc-codereview.appspot.com/24179004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7631 4adac7df-926f-26a2-2b94-8c16560cd09d