linux-aura: Fix some dragging behaviour.

Do a proper X11 grab on capture. This fixes a number of issues, including
dragging a tab out of a tabstrip, and then dragging it back in.

BUG=318020
R=erg@chromium.org

Review URL: https://codereview.chromium.org/110223004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241160 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241160
cros: Polish SAML signin.

- Show 'Cancel' button on footer bar when SAML is active;
- Add a message on top of sign-in frame when redirected to saml idp page;
- Use logo and padding as signin screen for confirm password and no password
  screen;

BUG=307202
EST=Browser tests SamlTest.*.

Review URL: https://codereview.chromium.org/70763002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241161 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241161