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..5cd732f93485c87a977116f7719aca6b37e06cf6 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();
 
       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 +46,28 @@
 
       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': 0.000001})", function () {
+        context = new AudioContext({'latencyHint': 0.000001});
+      }).notThrow();
+      Should("double-constructor baseLatency small", context.baseLatency).beEqualTo(defaultLatency);
+      context.close();
+
+      // Verify that exact latency in range works as expected
+      Should("context = new AudioContext({'latencyHint': 0.01})", function () {
+        context = new AudioContext({'latencyHint': 0.01});
+      }).notThrow();
+      Should("double-constructor baseLatency ok", context.baseLatency).beEqualTo(0.02);

[Raymond Toy, 2017/03/14 15:19:39]

Doesn't this really depend on the actual sampleRate of the audio context?  I run
the layout tests in a browser all the time, and the context sample rate changes
quite a bit when I'm experimenting.  Usually 44.1 or 48 kHz, but I sometimes use
88.2, 96, or even 192.

[Andrew MacPherson, 2017/03/15 15:08:17]

Hmm, I think I may not understand where the values here come from then. I
thought that the sample rate was always the one provided in the
layout_test_content_renderer_client.cc but I can take a closer look. Agreed that
the code is sloppy though, I've refactored it to use numbers based on existing
known latency type values rather than these hardcoded ones.

+      context.close();
+
+      // Verify too big exact latency clamped to 'playback'
+      Should("context = new AudioContext({'latencyHint': 5})", function () {

[Raymond Toy, 2017/03/14 15:19:39]

Nit: I think it would be slightly better to compute this instead of a fixed 5. 
Use something like 2*playbackLatency or something definitely bigger than
playbackLatency.

[Andrew MacPherson, 2017/03/15 15:08:18]

Done!

+        context = new AudioContext({'latencyHint': 5});
+      }).notThrow();
+      Should("double-constructor baseLatency big", context.baseLatency).beEqualTo(playbackLatency);
+      context.close();
 
       // Verify that invalid latencyHint values are rejected.
       Should("context = new AudioContext({'latencyHint': 'foo'})", function () {