Trigger full html.css styles for some printing tests.

Trigger full html.css styles for some printing tests.

In Blink, @page UA styles is missing from the simple html stylesheet which
is used instead of html.css for documents which contains a certain subset
of html element types. Adding that @page rule to that simplified stylesheet
will change the actual results for these tests which have expectations
relying on that bug[1]:

  PrintWebViewHelperPreviewTest.PrintPreviewShrinkToFitPage
  PrintWebViewHelperPreviewTest.PrintPreviewCenterToFitPage

This CL changes the expected results and adds a <p> element to those tests
in order to trigger the correct @page rule from html.css without the fix in
Blink. Then the Blink fix[2] can land and be rolled into chromium without
affecting the results of the mentioned tests.

After the Blink fix is rolled into chromium, the <p> elements can be safely
removed again.

[1] https://code.google.com/p/chromium/issues/detail?id=304021
[2] https://codereview.chromium.org/25856002/

R=vitalybuka@chromium.org
BUG=304021

Review URL: https://codereview.chromium.org/25446005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227076 0039d316-1c4b-4281-b951-d872f2087c98