Add use counter for web file system

This CL adds three use counters for file system to see how often the feature is
used on the main thread, in workers, and synchronously in workers.

R=esprehn@chromium.org

Review URL: https://codereview.chromium.org/426343002

git-svn-id: svn://svn.chromium.org/blink/trunk@179264 bbb929c8-8fbe-4397-9dbb-9b2b20218538
RenderBlock::layoutPositionedObjects shouldn't call setNeedsLayoutAndFullPaintInvalidation

There's no need to do a full paint invalidation at this time. We can just call
setNeedsLayout instead.

R=jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/429363002

git-svn-id: svn://svn.chromium.org/blink/trunk@179265 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[DevTools] Fix MediaQueryInspector not working in toolbox.

BUG=none
TBR=apavlov

Review URL: https://codereview.chromium.org/433443004

git-svn-id: svn://svn.chromium.org/blink/trunk@179266 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make collection caching code more consistent

Make collection caching code more consistent by:
- Moving ensureCachedHTMLCollection() from Document and Element to
  ContainerNode and renaming it to ensureCachedCollection().
- Make ensureCachedCollection() templated to avoid if checks on the type in
  the implementation and to avoid casting the return value at the call sites.
- Use ensureCachedCollection() more consistently in the code base. Half the
  code was calling NodeListsNodeData::addCache<>() directly.

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

Review URL: https://codereview.chromium.org/342283005

git-svn-id: svn://svn.chromium.org/blink/trunk@179267 bbb929c8-8fbe-4397-9dbb-9b2b20218538