Update chromium.googlesource.com URL to refer to the correct branch. (#1853)
Update chromium.googlesource.com URL to refer to the correct branch. (#1853)

This fixes a references to the old name of the Chromium repository's main branch in our source code.
GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard,GoogleChrome/chromium-dashboard