IDL: Use user-friendly type names for error messages

This is a follow-up CL of https://codereview.chromium.org/690923004/.

It would be great to show "(A or B)" rather than "AOrB".

BUG=240176

Review URL: https://codereview.chromium.org/722523003

git-svn-id: svn://svn.chromium.org/blink/trunk@185195 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/fast/events/constructors/track-event-constructor-expected.txt

@@ -15,15 +15,15 @@ PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true }).cancelabl
 PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true }).track is null
 
 *** Bubbles and cancelable true, invalid track ***
-PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true, track: HTMLTrackElement }).bubbles threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a VideoTrackOrAudioTrackOrTextTrack type..
-PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true, track: HTMLTrackElement }).cancelable threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a VideoTrackOrAudioTrackOrTextTrack type..
-PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true, track: HTMLTrackElement }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a VideoTrackOrAudioTrackOrTextTrack type..
+PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true, track: HTMLTrackElement }).bubbles threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a (VideoTrack or AudioTrack or TextTrack) type..
+PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true, track: HTMLTrackElement }).cancelable threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a (VideoTrack or AudioTrack or TextTrack) type..
+PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true, track: HTMLTrackElement }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a (VideoTrack or AudioTrack or TextTrack) type..
 
 *** Initialize 'track' with a invalid values ***
-PASS new TrackEvent('TrackEvent', { track: 10 }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a VideoTrackOrAudioTrackOrTextTrack type..
-PASS new TrackEvent('TrackEvent', { track: 'string' }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a VideoTrackOrAudioTrackOrTextTrack type..
-PASS new TrackEvent('TrackEvent', { track: emptyObject }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a VideoTrackOrAudioTrackOrTextTrack type..
-PASS new TrackEvent('TrackEvent', { track: document }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a VideoTrackOrAudioTrackOrTextTrack type..
+PASS new TrackEvent('TrackEvent', { track: 10 }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a (VideoTrack or AudioTrack or TextTrack) type..
+PASS new TrackEvent('TrackEvent', { track: 'string' }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a (VideoTrack or AudioTrack or TextTrack) type..
+PASS new TrackEvent('TrackEvent', { track: emptyObject }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a (VideoTrack or AudioTrack or TextTrack) type..
+PASS new TrackEvent('TrackEvent', { track: document }).track threw exception TypeError: Failed to construct 'TrackEvent': The 'track' property does not have a (VideoTrack or AudioTrack or TextTrack) type..
 
 *** Bubbles and cancelable true, valid track ***
 PASS new TrackEvent('TrackEvent', { bubbles: true, cancelable: true, track: trackElement.track }).bubbles is true

third_party/WebKit/Source/bindings/scripts/idl_types.py

@@ -253,7 +253,7 @@ class IdlUnionType(IdlTypeBase):
         self.member_types = member_types
 
     def __str__(self):
-        return self.name
+        return '(' + ' or '.join(str(member_type) for member_type in self.member_types) + ')'
 
     def __hash__(self):
         return hash(self.name)