DevTools: center emulated device view inside available view space.

This also removes deprecated |enableDeviceEmulation| implementation.

BUG=317602,315095

Review URL: https://codereview.chromium.org/68713002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234512 0039d316-1c4b-4281-b951-d872f2087c98
Android: moves native_test to use long for JNI

BUG=317523

Review URL: https://codereview.chromium.org/70123002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234513 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234512
SVN changes up to revision 234513