Remove '?' from dictionary members of DeviceMotionEventInit

It is invalid for a WebIDL dictionary member that resolves to a nullable
type to be marked with '?'. This change is effectively a no-op because
these fields remain nullable.

This patch implements the changes to the specification in:
https://github.com/w3c/deviceorientation/pull/55

Change-Id: I43222ec37ec216f8cb2932aedbddfb307ec4374f
Reviewed-on: https://chromium-review.googlesource.com/c/1239722
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609930}

third_party/WebKit/LayoutTests/device_orientation/motion/optional-event-properties.html

@@ -175,9 +175,15 @@ test(test => {
                                      accelerationIncludingGravity: null,
                                      rotationRate: null,
                                      interval: null});
-  assert_equals(event.acceleration, null);
-  assert_equals(event.accelerationIncludingGravity, null);
-  assert_equals(event.rotationRate, null);
+  assert_equals(event.acceleration.x, null);
+  assert_equals(event.acceleration.y, null);
+  assert_equals(event.acceleration.z, null);
+  assert_equals(event.accelerationIncludingGravity.x, null);
+  assert_equals(event.accelerationIncludingGravity.y, null);
+  assert_equals(event.accelerationIncludingGravity.z, null);
+  assert_equals(event.rotationRate.alpha, null);
+  assert_equals(event.rotationRate.beta, null);
+  assert_equals(event.rotationRate.gamma, null);
   assert_equals(event.interval, 0);
 }, "Tests all values are null.");
 

third_party/blink/renderer/modules/device_orientation/device_motion_event_init.idl

@@ -5,8 +5,8 @@
 // https://w3c.github.io/deviceorientation/spec-source-orientation.html#devicemotion
 
 dictionary DeviceMotionEventInit : EventInit {
-  DeviceAccelerationInit? acceleration;
-  DeviceAccelerationInit? accelerationIncludingGravity;
-  DeviceRotationRateInit? rotationRate;
+  DeviceAccelerationInit acceleration;
+  DeviceAccelerationInit accelerationIncludingGravity;
+  DeviceRotationRateInit rotationRate;
   double interval = 0;
 };