WebMidi: stop using testRunner.setMIDISysexPermision and remove ClientMock.

LayoutTests/webmidi/send-messages.html

Index: LayoutTests/webmidi/send-messages.html
diff --git a/LayoutTests/webmidi/send-messages.html b/LayoutTests/webmidi/send-messages.html
index bdb6dac086123560608d5a1bb31cebe78211bf47..075b7eb1f548eee09d2452acc945947680ac8dbd 100644
--- a/LayoutTests/webmidi/send-messages.html
+++ b/LayoutTests/webmidi/send-messages.html
@@ -9,13 +9,11 @@
 description("Test if various kinds of MIDI messages can be validated.");
 
 shouldBeDefined("testRunner.setPermission");
-shouldBeDefined("testRunner.setMIDISysexPermission");
 shouldBeDefined("navigator.requestMIDIAccess");
 
 window.jsTestIsAsync = true;
 
 testRunner.setPermission('midi-sysex', 'granted', location.origin, location.origin);
-testRunner.setMIDISysexPermission(true);
 
 navigator.requestMIDIAccess({sysex: true}).then(function (a) {
     output = a.outputs.values().next().value;