Have getChildNodes() take a ContainerNode in argument

Have getChildNodes() take a ContainerNode in argument instead of a Node as
this utility function only makes sense for ContainerNodes. Also, this lets
the compiler generate slighter more efficient code.

This CL also makes use of getChildNodes() in more places to avoid code
duplication.

R=adamk@chromium.org

Review URL: https://codereview.chromium.org/435733002

git-svn-id: svn://svn.chromium.org/blink/trunk@179356 bbb929c8-8fbe-4397-9dbb-9b2b20218538
MSE: Fix flaky mediasource-append-buffer.html test

Media source specification's end of stream algorithm is currently
underspecified when no media data is buffered, and implementation may
transition beyond 'ended' to 'closed' MediaSource readyState.

This change updates the layout test to cover the well-specified case
when there is media data buffered prior to endOfStream() and removes the
flaky fail expectation. Later tests will be added to cover the currently
underspecified cases, once correct behavior is defined and implemented.

BUG=399188
R=acolwell@chromium.org
TEST=mediasource-append-buffer.html passed 100/100 attempts with 8 content_shells in parallel locally on linux

Review URL: https://codereview.chromium.org/417163006

git-svn-id: svn://svn.chromium.org/blink/trunk@179357 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move Node/ContainerNode's traverseToChildAt() to NodeTraversal

Move Node/ContainerNode's traverseToChildAt() to NodeTraversal and rename to
childAt() as this method does DOM Tree traversal and we already have a utility
class for this.

R=adamk@chromium.org

Review URL: https://codereview.chromium.org/425223005

git-svn-id: svn://svn.chromium.org/blink/trunk@179358 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: Replace TreeScope& in TreeScopeStyleSheetCollection with RawPtrWillBeMember<TreeScope>

BUG=340522

Review URL: https://codereview.chromium.org/438743002

git-svn-id: svn://svn.chromium.org/blink/trunk@179359 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Oilpan: Move VisitedLinkState to oilpan's heap

BUG=340522

Review URL: https://codereview.chromium.org/421723003

git-svn-id: svn://svn.chromium.org/blink/trunk@179360 bbb929c8-8fbe-4397-9dbb-9b2b20218538