Add audible, muted to Tab, c.t.query, c.t.update, and c.t.onUpdated where relevant

chrome/test/data/extensions/api_test/tabs/basics/sinewave.js

+// Copyright (c) 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+function enableSineWave() {
+  var freqs = [200, 500, 1800];
+  var curTestIdx = 0;

[not at google - send to devlin, 2015/06/01 20:33:57]

am I missing something, or is curTestIdx never actually changed?

(btw should be currentTextIdx or currentTextIndex or even testIndex or whatever
- point being, minimise abbreviations, unless it's a super common one, often
used to avoid a collision with a keyword or whatever - I'm guilty of using
"obj").

[Jared Sohn, 2015/06/02 08:54:38]

Just a note on this: I didn't write most of this code (it came from
/src/chrome/test/data/extensions/api_test/cast_streaming/end_to_end_sender.js&l=54)
but I should have cleaned it up more (especially in terms of what portions I
copied over).

Code rewritten.

+  if (!this.audioContext) {
+    this.audioContext = new AudioContext();

[not at google - send to devlin, 2015/06/01 20:33:56]

I'd rather not use |this| here. Trivia: it actually used to be the case that
using |this| here wouldn't work, because v8 would set it to the *calling*
window, not the *receiver* window. So, doing

getOnlyTab().enableSineWave();

would call enableSinceWave on the current window (i.e. the background page), not
the tab. Anyway, that's fixed, but looking at this file in isolation is pretty
hard to see what's going on. The variables you're setting on it also seem
dangerously prone to being overridden.

If this were production code or something you could do something more fancy than
this, but I'd approximate modularity like:

An approximation of JS modularity would look like:

window.sinewave = {
  enable: function(win) {
    var data = win.sinewaveData_;
    if (!data) {
      data = {};
      win.sinewaveData_ = data;
    }
    if (!data.audioContext) ... etc ...;
    if (!data.oscillator...) ... etc ...;
  },

  disable: function(obj) {
    obj.sinewave_.oscillator.stop();
  }
};

then the places where you call getOnlyTab().enableSineWave() you'd instead call
window.sinewave.enable(getOnlyTab()), and you only need to include the
sinewave.js file on the background page.

[Jared Sohn, 2015/06/02 08:54:38]

Done.

+    this.gainNode = this.audioContext.createGain();
+    this.gainNode.gain.value = 0.5;
+    this.gainNode.connect(this.audioContext.destination);
+  }
+  if (!this.oscillator ||
+      this.oscillator.frequency.value != freqs[curTestIdx]) {
+    // Note: We recreate the oscillator each time because this switches the
+    // audio frequency immediately.  Re-using the same oscillator tends to take
+    // several hundred milliseconds to ramp-up/down the frequency.
+    if (this.oscillator) {
+      this.oscillator.stop();
+      this.oscillator.disconnect();
+    }
+    this.oscillator = this.audioContext.createOscillator();
+    this.oscillator.type = OscillatorNode.SINE;
+    this.oscillator.frequency.value = freqs[curTestIdx];
+    this.oscillator.connect(this.gainNode);
+    this.oscillator.start();
+  }
+}
+
+function disableSineWave() {
+  this.oscillator.stop();
+}