Don't use adjustedFocusedElement in order to blur the focused element when removing a node.

This makes http://jsperf.com/parse-html-type (micro benchmarks for innerHTML) 35% faster.
87k ops/s vs. 64k ops/s on the "tags" test on my machine. Other tests get similar performance gain too.

We don't have to use adjustedFocusedElement() in Document::removeFocusedElementInSubtree(). TreeScope::adjustedFocusedElement() is a costly operation

The reason of calling adjustedFocusedElement() until now is:
- When a distributed node is focused and its final destination insertion point, for example, is removed, we want to guarantee that the focused distributed node is blurred correctly.

But this case is similar to setting 'display: none;' to the focused element in a sense that the focused element stays in document, but it doesn't get rendered anymore.

We don't guarantee this behavior. We leave the focused element as document.activeElement in this case. Other browsers (old Opera, Firefox, WebKit) does so.

See also the discussion starting https://code.google.com/p/chromium/issues/detail?id=318448#c23.


BUG=318448

Review URL: https://codereview.chromium.org/72303003

git-svn-id: svn://svn.chromium.org/blink/trunk@162099 bbb929c8-8fbe-4397-9dbb-9b2b20218538