Improve detection of touch events when hiding media controls.

We propagate synthetic state down from PlatformMouseEvent
into MouseEvent / MediaControls instead of relying on
whether the platform does not support a mouse. This allows
us to hide the controls after touch even in those platforms
that support a mouse.

We rename NotFromTouch to RealOrIndistinguishable in
preparation for adding new values, for example to replace
isSimulated.

BUG=401177

Review URL: https://codereview.chromium.org/453493002

git-svn-id: svn://svn.chromium.org/blink/trunk@181055 bbb929c8-8fbe-4397-9dbb-9b2b20218538