Adding transitions when the print preview is loading.
1) When a preview is being rendered, the old print preview is faded out.
2) A "Loading preview ..." message is shown (with the dots dancing!).
3) The new preview is faded in once it becomes available.
Also in this CL, some unused css rules have been removed.
BUG=NONE
TEST=Open a very large document in the preview, make changes to the settings
and observe the transitions.
Review URL: http://codereview.chromium.org/
6896033
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@82749 0039d316-1c4b-4281-b951-d872f2087c98