Moved PinchViewport from WebViewImpl to FrameHost.

BUG=349941

Review URL: https://codereview.chromium.org/192523003

git-svn-id: svn://svn.chromium.org/blink/trunk@169074 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Enabled Navigator.maxTouchPoints without flag in stable.

Feature Dashboard: http://www.chromestatus.com/features/4504699138998272
Intent to ship: https://groups.google.com/a/chromium.org/forum/#!searchin/blink-dev/maxTouchPoints/blink-dev/ayzxdztUlOQ/rd-z_Jo3ocIJ

BUG=308649

Review URL: https://codereview.chromium.org/192873002

git-svn-id: svn://svn.chromium.org/blink/trunk@169075 bbb929c8-8fbe-4397-9dbb-9b2b20218538