Remove indirect pure virtual call from destructor of DeviceSensorEventController.

Pure virtual methods should not be called from a destructor.
Such calls can result in crashes.

BUG=316317

Review URL: https://codereview.chromium.org/99483010

git-svn-id: svn://svn.chromium.org/blink/trunk@163277 bbb929c8-8fbe-4397-9dbb-9b2b20218538