DevTools: added layer details view

Added a view to display layer details (dimensions, memory usage, compositing reasons)
Drive-by: added visual indication of hidden layers, renamed storage-empty-view to just
empty-view.

BUG=279048
R=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/22908013

git-svn-id: svn://svn.chromium.org/blink/trunk@156713 bbb929c8-8fbe-4397-9dbb-9b2b20218538