It seems that we don't need this member anymore, since all TouchView-enabled devices have the #ash-enable-touch-view flag. 

The below comment will be removed as part of removing the #ash-touch-view-testing flag in https://codereview.chromium.org/2642853006/ included here for reference.

bool MaximizeModeController::CanEnterMaximizeMode() {
  // If we have ever seen accelerometer data, then HandleHingeRotation may
  // trigger maximize mode at some point in the future.
  // The --enable-touch-view-testing switch can also mean that we may enter
  // maximize mode.
  // TODO(mgiuca): This can result in false positives, as it returns true for
  // any device with an accelerometer. Have TouchView-enabled devices explicitly
  // set a flag, and change this implementation to simply return true iff the
  // flag is present ( http://crbug.com/457445 ).
  return have_seen_accelerometer_data_ ||
         base::CommandLine::ForCurrentProcess()->HasSwitch(
             switches::kAshEnableTouchViewTesting);
}