Convert all synthetic gesture coordinates from CSS pixels to DIPs.

There is currently some inconsistency about the units of pixels being passed to
synthetic gestures, some are CSS pixels and some are density independent pixels
(DIPs). The internal classes expect DIPs but the scroll distance is being
passed in CSS pixels, causing us to scroll too far on pages with page scale
factors > 1.

This patch clarifies the interface between the JS functions for gestures and the
internal classes. The JS functions expect coordinates to be in CSS pixels which
are then converted to DIPs before being passed to the gesture objects.

BUG=313669

Review URL: https://codereview.chromium.org/56093002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233677 0039d316-1c4b-4281-b951-d872f2087c98
Allow GrabWindowSnapshot() to fail when libpng fails.

BUG=280195
R=sky@chromium.org, kinaba@chromium.org
TEST=None

Review URL: https://codereview.chromium.org/59073011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233678 0039d316-1c4b-4281-b951-d872f2087c98
Don't reopen a signed out profile if it was the last active profile

The possible scenarios this CL is addressing are:
- if the last and only active profile was signed out/guest, 
don't re-open it and open the User Manager instead
- if you're re-opening a bunch of profiles, one of which is 
guest, then just skip opening the guest one
- the signed out case does not apply above, as upon signing 
out all browser windows for the profile are closed, so when 
quitting chrome, this profile won't count as having any open 
browsers

BUG=315131
TEST=With --new-profile-management enabled, do one of the 
following: 1. Sign in a profile and make sure no other 
profiles are opened. Once sign-in is complete, press "Sign 
out" or 2. Start a guest mode profile (and close any other 
opened profiles). In both of these cases, close Chrome and 
re-start it. You should see the User Manager screen and not a
browser for the signed out/guest profile.

Review URL: https://codereview.chromium.org/59103011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233679 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233678
Moves some files into mojo/common

BUG=none
TEST=none
R=darin@chromium.org, viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/64973002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233680 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233680