Have NodeList::item() overrides return an Element* when appropriate

Have NodeList::item() overrides return an Element* when appropriate instead
of a generic Node*. This makes it clear to callers that these are actually
returning Elements and avoids unnecessary isElementNode() checks or casts
that look unsafe.

R=adamk@chromium.org, esprehn@chromium.org

Review URL: https://codereview.chromium.org/331863003

git-svn-id: svn://svn.chromium.org/blink/trunk@176239 bbb929c8-8fbe-4397-9dbb-9b2b20218538
HTML Imports: Add an UseCounter for <link rel=import async>

TEST=none
BUG=383749
R=dglazkov@chromium.org

Review URL: https://codereview.chromium.org/334263005

git-svn-id: svn://svn.chromium.org/blink/trunk@176240 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix audit_runtime_enabled_features now that omahaproxy has headers in their CSV

BUG=371746

Review URL: https://codereview.chromium.org/339703002

git-svn-id: svn://svn.chromium.org/blink/trunk@176241 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Allow proper highlighting on universal overflow scroll.

Universal accelerated overflow scroll doesn't paint
highlight gaps between scroll children because the
scrolling contents layer isn't always set up to
draw content.

BUG=381185,381187

Review URL: https://codereview.chromium.org/303253004

git-svn-id: svn://svn.chromium.org/blink/trunk@176243 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[DirectWrite] Force fully aliased text for certain fonts at small sizes

Force the use of fully aliased text for certain common east asian fonts
at smaller font sizes to ensure that text is legible. This is only
required for fonts without an embedded bitmap at a the specific size and
the minimum size for enabling anti aliasing is set on a per font basis.

BUG=383090,383040
R=dglazkov@chromium.org, cpu@chromium.org

Review URL: https://codereview.chromium.org/339693002

git-svn-id: svn://svn.chromium.org/blink/trunk@176244 bbb929c8-8fbe-4397-9dbb-9b2b20218538