Created browser test for first-run UI.

BUG=312474
TEST=browser_tests --gtest_filter=FirstRunUIBrowserTest.*

Review URL: https://codereview.chromium.org/101543008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241933 0039d316-1c4b-4281-b951-d872f2087c98
Check for null web_contents in ThreeDAPIObserver::DidBlock3DAPIs().

This was one of the first places to fall over with a prototype IPC fuzzer. I've
added the check to bring the code into conformance with other caller of GetWebContentsById()

BUG=329664
R=jhawkins@chromium.org

Review URL: https://codereview.chromium.org/118703002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241934 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241934