Display pixel value in Device Emulation

Slider generates both oninput and onchange value.

R=pfeldman, tkent
BUG=346633

Review URL: https://codereview.chromium.org/179743002

git-svn-id: svn://svn.chromium.org/blink/trunk@167863 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Reduce HTMLMediaElement BehaviorRestrictions to a single state bit

There's only a single restriction left, so make it more obvious.

Although not the main purpose, this reduces sizeof(HTMLMediaElement) by
4 bytes, from 584 to 580 on Mac Debug.

BUG=none

Review URL: https://codereview.chromium.org/177123006

git-svn-id: svn://svn.chromium.org/blink/trunk@167864 bbb929c8-8fbe-4397-9dbb-9b2b20218538