GitLab

There are typically only a few events in a given gesture packet.  Avoid heap
allocating in the common case by switching from a raw vector to a StackVector.

BUG=395168

Review URL: https://codereview.chromium.org/403173004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284728 0039d316-1c4b-4281-b951-d872f2087c98