Have Position deal with more references

Have Position deal with more references instead of pointers. This makes the
code look safer.

R=adamk

Review URL: https://codereview.chromium.org/188033005

git-svn-id: svn://svn.chromium.org/blink/trunk@168675 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert 168384 "Use OwnPtrs for heap contains cache and persisten..."

Revert 168384 as it caused a serious crash (top #1 crasher on mac).

BUG=349842

> Use OwnPtrs for heap contains cache and persistent anchor. We were leaking the HeapContainsCache.
> 
> R=haraken@chromium.org, vegorov@chromium.org
> BUG=348629
> NOTRY=true
> 
> Review URL: https://codereview.chromium.org/183683017

TBR=ager@chromium.org

Review URL: https://codereview.chromium.org/180723022

git-svn-id: svn://svn.chromium.org/blink/trunk@168676 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Skip the invalid and flaky networkState_during_progress.html W3C test.

Per the bug discussion, this test is invalid. Since it is part of third party
tests, we must wait for it to be removed upstream. In the meantime, skip it.

BUG=306249
R=philipj@opera.com

Review URL: https://codereview.chromium.org/184233008

git-svn-id: svn://svn.chromium.org/blink/trunk@168677 bbb929c8-8fbe-4397-9dbb-9b2b20218538