Add comment explaining the reason why unittests are compiled in webkit build rule

BUG=

Review URL: https://chromiumcodereview.appspot.com/23039011

git-svn-id: svn://svn.chromium.org/blink/trunk@157105 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Return Frame&, not Frame* from RenderView::frame()

R=tkent@chromium.org
BUG=

Review URL: https://codereview.chromium.org/23728003

git-svn-id: svn://svn.chromium.org/blink/trunk@157106 bbb929c8-8fbe-4397-9dbb-9b2b20218538