Pause drawing when not visible
Pause drawing when not visible

 Bug: 5594608
 If onPause is called or if the view or view's window is no longer
 visible, pause webview drawing. Calls to onDraw will continue to work,
 but animations and other continual drawing will stop

Change-Id: I11640f087852d1a9a33b945ff72297fab1d25b94

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base