Don't enforce name rule for RTCDTMFToneChangeEvent

Since the constructor of RTCDTMFToneChangeEvent is exposed,
creating such events with other names than "tonechange" is possible.
No reason to discriminate against such.

Also adds tests for constructor.

Bug: chromium:822799
Change-Id: I4b36f3094acee200dd4200c4d24f6b46e10a06e6
Reviewed-on: https://chromium-review.googlesource.com/992038Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Harald Alvestrand <hta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547742}

third_party/WebKit/LayoutTests/external/wpt/webrtc/RTCDTMFSender-ontonechange.https-expected.txt

@@ -10,5 +10,7 @@ PASS Calling insertDTMF() in the middle of tonechange events should cause future
 PASS Calling insertDTMF() multiple times in the middle of tonechange events should cause future tonechanges to be updated the last provided tones
 PASS Calling insertDTMF('') in the middle of tonechange events should stop future tonechange events from firing
 FAIL Setting transceiver.currentDirection to recvonly in the middle of tonechange events should stop future tonechange events from firing pc.addTransceiver is not a function
+PASS Tone change event constructor works
+PASS Tone change event with unexpected name should not crash
 Harness: the test ran to completion.
 

third_party/WebKit/LayoutTests/external/wpt/webrtc/RTCDTMFSender-ontonechange.https.html

@@ -282,4 +282,15 @@
 
   }, `Setting transceiver.currentDirection to recvonly in the middle of tonechange events should stop future tonechange events from firing`);
 
+  /* Section 7.3 - Tone change event */
+  test(t => {
+    let ev = new RTCDTMFToneChangeEvent('tonechange', {'tone': '1'});
+    assert_equals(ev.type, 'tonechange');
+    assert_equals(ev.tone, '1');
+  }, 'Tone change event constructor works');
+
+  test(t => {
+    let ev = new RTCDTMFToneChangeEvent('worngname', {});
+  }, 'Tone change event with unexpected name should not crash');
+
 </script>

third_party/WebKit/Source/modules/peerconnection/RTCDTMFToneChangeEvent.cpp

@@ -34,7 +34,6 @@ RTCDTMFToneChangeEvent* RTCDTMFToneChangeEvent::Create(const String& tone) {
 RTCDTMFToneChangeEvent* RTCDTMFToneChangeEvent::Create(
     const AtomicString& type,
     const RTCDTMFToneChangeEventInit& initializer) {
-  DCHECK(type == EventTypeNames::tonechange);
   return new RTCDTMFToneChangeEvent(initializer);
 }