Use wheel events instead of mousewheel events in telemetry tests

Use wheel events instead of mousewheel events in the telemetry tests
since the latter are deprecated and no longer work with synthetic
gestures (all the deltas are zero).

BUG=307841

Review URL: https://codereview.chromium.org/114053003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240672 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240672
Add experimental flag to enable Chromecast in about:flags

BUG=326212

NOTRY=true

Review URL: https://codereview.chromium.org/99053006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240673 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240673