Clear pending frames when we receive a Page.navigate event from devtools, which fixes testShouldReturnWhenGettingAUrlThatDoesNotConnect

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/224903014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261946 0039d316-1c4b-4281-b951-d872f2087c98
[chromedriver] Use a longer partial filename so that we don't pull in false filename matches

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/226913003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261991 0039d316-1c4b-4281-b951-d872f2087c98