[Activity Log] Add a test case for logging webkitRequestFullscreen

Add a test case for the logging of the Element.webkitRequestFullscreen DOM
method added in https://codereview.chromium.org/23981009/.

BUG=289569

Review URL: https://codereview.chromium.org/23519016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225334 0039d316-1c4b-4281-b951-d872f2087c98
Add Content-Length header to component extension url responses 

When investigating the bug referenced below, we found that playing audio via
an <audio> tag from a file inside an extension worked if the extension was
installed normally, but not if it was a component extension. It turns out that
sending a Content-Length header makes this work properly.

BUG=284815

Review URL: https://codereview.chromium.org/23600029

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225335 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225335