Roll chromium_revision 8d51d96..bd49b12 (320682:320783)

Pulls in new libvpx version that allows us to re-enable the
VideoProcessorIntegrationTest.ProcessNoLossDenoiserOnVP9
test in webrtc/modules/video_coding/codecs/test/videoprocessor_integrationtest.cc

Relevant changes:
* src/third_party/libvpx: 763fe7a..f80cf58
* src/tools/gyp: 4a9b712..d174d75
Details: https://chromium.googlesource.com/chromium/src/+/8d51d96..bd49b12/DEPS

Clang version was not updated in this roll.

BUG=4418
TBR=marpan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/41339004

Cr-Commit-Position: refs/heads/master@{#8745}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8745 4adac7df-926f-26a2-2b94-8c16560cd09d