Support AudioContextOptions latencyHint as double.

third_party/WebKit/LayoutTests/webaudio/audiocontextoptions.html

Index: third_party/WebKit/LayoutTests/webaudio/audiocontextoptions.html
diff --git a/third_party/WebKit/LayoutTests/webaudio/audiocontextoptions.html b/third_party/WebKit/LayoutTests/webaudio/audiocontextoptions.html
index fe5e714bec6aa3949121c1b519bbaaa3264209ae..a377d1a31eedf9f8385d2a10065a0f8da8043ac1 100644
--- a/third_party/WebKit/LayoutTests/webaudio/audiocontextoptions.html
+++ b/third_party/WebKit/LayoutTests/webaudio/audiocontextoptions.html
@@ -23,12 +23,6 @@
       var defaultLatency = context.baseLatency;
       Should("default baseLatency", defaultLatency).beGreaterThan(0);
 
-      // Verify that any double can be passed and that it results in interactive latency
-      Should("context = new AudioContext({'latencyHint': 0.05})", function () {
-        context = new AudioContext({'latencyHint': 0.05});
-      }).notThrow();
-      Should("double-constructor baseLatency", context.baseLatency).beEqualTo(defaultLatency);
-
       // Verify that an AudioContext can be created with the expected latency types.
       Should("context = new AudioContext({'latencyHint': 'interactive'})", function () {
         context = new AudioContext({'latencyHint': 'interactive'});
@@ -36,6 +30,7 @@
 
       var interactiveLatency = context.baseLatency;
       Should("interactive baseLatency", interactiveLatency).beEqualTo(defaultLatency);
+      context.close();

[Raymond Toy, 2017/04/06 17:31:59]

Are we running out of online contexts without this?

close() returns a promise, so we might want to modify this so that the following
bits happen after the promise resolves.  Or move the following bits into its own
audit task which are run sequentially.

Same thing below wherever you call context.close().

[Andrew MacPherson, 2017/04/07 06:59:03]

Yes that's the reason for this. I've split the test into two audit tasks now
with less than 6 context created/closed in each, does that work?

 
       Should("context = new AudioContext({'latencyHint': 'balanced'})", function () {
         context = new AudioContext({'latencyHint': 'balanced'});
@@ -43,6 +38,7 @@
 
       var balancedLatency = context.baseLatency;
       Should("balanced baseLatency", balancedLatency).beGreaterThanOrEqualTo(interactiveLatency);
+      context.close();
 
       Should("context = new AudioContext({'latencyHint': 'playback'})", function () {
         context = new AudioContext({'latencyHint': 'playback'});
@@ -50,6 +46,34 @@
 
       var playbackLatency = context.baseLatency;
       Should("playback baseLatency", playbackLatency).beGreaterThanOrEqualTo(balancedLatency);
+      context.close();
+
+      // Verify too small exact latency clamped to 'interactive'
+      Should("context = new AudioContext({'latencyHint': interactiveLatency/4})", function () {
+        context = new AudioContext({'latencyHint': interactiveLatency/4});
+      }).notThrow();
+      Should("double-constructor baseLatency small", context.baseLatency).beEqualTo(defaultLatency);
+      context.close();
+
+      // Verify that exact latency in range works as expected
+      var validLatency = (interactiveLatency + playbackLatency) / 4;

[Raymond Toy, 2017/04/06 17:32:00]

Why divide by 4?  Don't you want to divide by 2 so you're definitely between
interactive and playback (in general)?

[Andrew MacPherson, 2017/04/07 06:59:03]

Currently AudioContext.baseLatency is returning the latency*2 to account for
double-buffering so I'm using 4 here, I agree that this is confusing though.
I've added a comment around the use of 4 rather than 2.

+      Should("context = new AudioContext({'latencyHint': validLatency})", function () {
+        context = new AudioContext({'latencyHint': validLatency});
+      }).notThrow();
+      Should("double-constructor baseLatency inrange 1", context.baseLatency).beGreaterThanOrEqualTo(defaultLatency);

[Raymond Toy, 2017/04/06 17:32:00]

defaultLatency or interactiveLatency?

[Andrew MacPherson, 2017/04/07 06:59:03]

Done.

+      Should("double-constructor baseLatency inrange 2", context.baseLatency).beLessThanOrEqualTo(playbackLatency);
+      context.close();
+
+      // Verify too big exact latency clamped to some value
+      var context1;
+      var context2;
+      Should("creating two high latency contexts", function () {
+        context1 = new AudioContext({'latencyHint': playbackLatency*2});
+        context2 = new AudioContext({'latencyHint': playbackLatency*20});
+      }).notThrow();
+      Should("high latency context baseLatency", context1.baseLatency).beEqualTo(context2.baseLatency);
+      context1.close();
+      context2.close();
 
       // Verify that invalid latencyHint values are rejected.
       Should("context = new AudioContext({'latencyHint': 'foo'})", function () {