[XHR] Abort method execution when m_loader->cancel() in internalAbort() caused reentry

Calling cancel() on DocumentThreadableLoader may results in calling
window.onload synchronously. If open(), send(), etc. are called on the same
XMLHttpRequest object, it'll be hard to resolve conflict of states without
losing spec conformance. This CL avoids that by just aborting execution of
code for the outer method that calls internalAbort() if it returns false.

BUG=292422

Review URL: https://chromiumcodereview.appspot.com/24304004

git-svn-id: svn://svn.chromium.org/blink/trunk@158146 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add use counter to document.all()

document.all is both a function and collection and it has a legacy
caller. The DOM spec is trying to figure out if this is required for
web compat.

BUG=None

Review URL: https://chromiumcodereview.appspot.com/23587027

git-svn-id: svn://svn.chromium.org/blink/trunk@158147 bbb929c8-8fbe-4397-9dbb-9b2b20218538