Update order of select events to match WebXR spec

The WebXR Spec requires that select events be fired in the order:
1) SelectStart
2) Select
3) SelectEnd

The current implementation in chrome flips the order of events 2 and 3.
This change flips that order to match the spec.

Bug: 960997
Change-Id: I3a8aca683898515102999d86b7bcee6c6e74ef24
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1607180
Commit-Queue: Brandon Jones <bajones@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Auto-Submit: Alexander Cooper <alcooper@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659727}

chrome/test/data/xr/e2e_test_files/html/test_webxr_input.html

@@ -21,7 +21,7 @@ that Daydream controller input is registered when using Daydream View.
       var finishAfterEachInput = true;
 
       function onSelectStart() {
-        // selectstart should always be fired first, so check that
+        // selectstart should always be fired first, so check that.
         assert_true(selectStartCount == selectEndCount,
                     'selectstart fired before selectend');
         assert_true(selectStartCount == selectCount,
@@ -29,22 +29,22 @@ that Daydream controller input is registered when using Daydream View.
         selectStartCount++;
       }
 
-      function onSelectEnd() {
-        // selectend should always be fired between selectstart and select
-        assert_true(selectEndCount + 1 == selectStartCount,
-                    'selectend fired after selectstart');
-        assert_true(selectEndCount == selectCount,
-                    'selectend fired before select');
-        selectEndCount++;
-      }
-
       function onSelect() {
-        // select should always be fired last
-        selectCount++;
-        assert_true(selectCount == selectStartCount,
+        // select should always be fired between selectstart and selectend.
+        assert_true(selectCount + 1 == selectStartCount,
                     'select fired after selectstart');
         assert_true(selectCount == selectEndCount,
                     'select fired after selectend');
+        selectCount++;
+      }
+
+      function onSelectEnd() {
+        // selectend should always be fired last.
+        selectEndCount++;
+        assert_true(selectEndCount == selectStartCount,
+                    'selectend fired after selectstart');
+        assert_true(selectEndCount == selectCount,
+                    'selectend fired before select');
         currentIteration++;
         if (currentIteration == iterations) {
           done();

third_party/blink/renderer/modules/xr/xr_session.cc

@@ -857,9 +857,6 @@ void XRSession::OnSelect(XRInputSource* input_source) {
     OnSelectStart(input_source);
   }
 
-  // Make sure we end the selection prior to firing the select event.
-  OnSelectEnd(input_source);
-
   if (!input_source->selection_cancelled) {
     XRInputSourceEvent* event =
         CreateInputSourceEvent(event_type_names::kSelect, input_source);
@@ -868,6 +865,8 @@ void XRSession::OnSelect(XRInputSource* input_source) {
     // Ensure the frame cannot be used outside of the event handler.
     event->frame()->Deactivate();
   }
+
+  OnSelectEnd(input_source);
 }
 
 void XRSession::OnPoseReset() {

third_party/blink/web_tests/xr/events_session_select.html

@@ -21,9 +21,9 @@ let requestSessionModes = ['immersive-vr'];
 
 let testFunction = function(session, t, fakeDeviceController) {
   let eventWatcher = new EventWatcher(
-    t, session, ["selectstart", "selectend", "select", "watcherdone"]);
+    t, session, ["selectstart", "select", "selectend", "watcherdone"]);
   let eventPromise = eventWatcher.wait_for(
-    ["selectstart", "selectend", "select", "watcherdone"]);
+    ["selectstart", "select", "selectend", "watcherdone"]);
 
   // Need to have a valid pose or input event's don't process.
   fakeDeviceController.setXRPresentationFrameData(VALID_POSE_MATRIX, [{
@@ -64,6 +64,7 @@ let testFunction = function(session, t, fakeDeviceController) {
       assert_equals(event.inputSource, input_sources[0]);
       tryCallingFrameMethods(event.frame);
     });
+    session.dispatchEvent(watcherDone);
   }
 
   function onSessionSelect(event) {
@@ -73,8 +74,8 @@ let testFunction = function(session, t, fakeDeviceController) {
       assert_equals(event.inputSource, input_sources[0]);
       tryCallingFrameMethods(event.frame);
     });
-    session.dispatchEvent(watcherDone);
   }
+
   session.addEventListener("selectstart", onSessionSelectStart, false);
   session.addEventListener("selectend", onSessionSelectEnd, false);
   session.addEventListener("select", onSessionSelect, false);