Add (url, transitionType) constructor to LoadUrlParams.java.

This patch allows to indicate page transition type when creating
LoadUrlParams.java instance. This supports a common use case of the
Chrome embedder where only url and transition type are set for a url
load.

BUG=346290

Review URL: https://codereview.chromium.org/185463006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254561 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254561