This CL attempts to improve upon the default loading priorities for images. By default, images will start at ResourceLoadPriorityVeryLow and after a layout or during a scroll, anything that's visible will be promoted up to ResourceLoadPriorityLow.

In our tests, this was a really nice win on speed-index, with a gain of ~5% on average, at ~14% at the 99th percentile.

BUG=319073

Review URL: https://codereview.chromium.org/86533002

git-svn-id: svn://svn.chromium.org/blink/trunk@163110 bbb929c8-8fbe-4397-9dbb-9b2b20218538
s/styleResolver/ensureStyleResolver and s/resolver/ensureResolver.

This is keeping with our naming convention to indicate that this
a) never returns null
b) does a lot of work

-got rid of one case where we were null checking: hasSelectorForAttribute.
-cleaned up a little code in Document::recalcStyle to only call
ensureStyleResolver once.

The rest is just a straight find and replace.

Review URL: https://codereview.chromium.org/102423003

git-svn-id: svn://svn.chromium.org/blink/trunk@163111 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Notify the embedder of v8::Context destruction before calling DetachGlobal()

This should reduce the chances of Blink or Chromium attempting to call
v8::Context::Global() after the global has been detached. In the long run,
the hope is to make calling Global() at that point an error, rather than
the current behavior of returning the raw global object.

It's also likely this will make the extensions code less weird, in that
it will be operating on a context that's in a reasonable state.

BUG=324812

Review URL: https://codereview.chromium.org/99983003

git-svn-id: svn://svn.chromium.org/blink/trunk@163112 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove TextTrackCue::isVTTCue

It is unused, as virtual functions are used instead of casting.

BUG=270340

Review URL: https://codereview.chromium.org/102003002

git-svn-id: svn://svn.chromium.org/blink/trunk@163113 bbb929c8-8fbe-4397-9dbb-9b2b20218538