Remove redundant checks for hasOwnProperty being defined

The method is always defined, no need for additional checks in inspector tests.

BUG=None

Review URL: https://codereview.chromium.org/486543003

git-svn-id: svn://svn.chromium.org/blink/trunk@180443 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Ignore fullscreen requests for the current fullscreen element

http://fullscreen.spec.whatwg.org/#dom-element-requestfullscreen

This spec change was made in order to simplify the fix for mis-nested
fullscreen in iframes:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=26568 (comments 9-13)

The requestFullscreen() implementation is not in sync with the spec, but
an early return is equivalent until the "run the remaining steps
asynchronously" bit is implemented.

In order to be affected by this change, one would have to request
fullscreen for the same element twice and do something meaningful in the
fullscreenerror event, which is likely rare.

Note that exitFullscreen() already does nothing if the fullscreen
element stack is empty, so there is some symmetry to this.

TEST=LayoutTests/fullscreen/api/element-request-fullscreen-top.html
TEST=LayoutTests/fullscreen/api/element-request-fullscreen-non-top.html

BUG=403741

Review URL: https://codereview.chromium.org/482543002

git-svn-id: svn://svn.chromium.org/blink/trunk@180444 bbb929c8-8fbe-4397-9dbb-9b2b20218538