Support AudioContextOptions latencyHint as double.

content/shell/renderer/layout_test/layout_test_content_renderer_client.cc

Index: content/shell/renderer/layout_test/layout_test_content_renderer_client.cc
diff --git a/content/shell/renderer/layout_test/layout_test_content_renderer_client.cc b/content/shell/renderer/layout_test/layout_test_content_renderer_client.cc
index 163a7415b668fbde8e687b746139672b7daec63f..2968807cf9bdd2cf86ecdfa8fb0b8a1ea8737d97 100644
--- a/content/shell/renderer/layout_test/layout_test_content_renderer_client.cc
+++ b/content/shell/renderer/layout_test/layout_test_content_renderer_client.cc
@@ -32,6 +32,7 @@
 #include "content/test/mock_webclipboard_impl.h"
 #include "gin/modules/module_registry.h"
 #include "media/media_features.h"
+#include "third_party/WebKit/public/platform/WebAudioLatencyHint.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamCenter.h"
 #include "third_party/WebKit/public/web/WebFrameWidget.h"
 #include "third_party/WebKit/public/web/WebKit.h"
@@ -194,10 +195,33 @@ LayoutTestContentRendererClient::OverrideCreateMIDIAccessor(
   return interfaces->CreateMIDIAccessor(client);
 }
 
-WebAudioDevice* LayoutTestContentRendererClient::OverrideCreateAudioDevice() {
+WebAudioDevice* LayoutTestContentRendererClient::OverrideCreateAudioDevice(
+    const blink::WebAudioLatencyHint& latency_hint) {
+  const double hw_buffer_size = 128;
+  const double hw_sample_rate = 44100;

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

Where do these numbers come from?  And why these particular values?

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

These are completely arbitrary, my understanding is that the WebAudioDevice has
its own default hardware sample rate and buffer size so this is creating a mock
of a device that has these particular values. Would there be a better way to
handle this?

+  double buffer_size = 0;
+  switch (latency_hint.category()) {
+    case blink::WebAudioLatencyHint::kCategoryInteractive:
+      buffer_size = hw_buffer_size;
+      break;
+    case blink::WebAudioLatencyHint::kCategoryBalanced:
+      buffer_size = hw_buffer_size * 2;
+      break;
+    case blink::WebAudioLatencyHint::kCategoryPlayback:
+      buffer_size = hw_buffer_size * 4;
+      break;
+    case blink::WebAudioLatencyHint::kCategoryExact:
+      buffer_size = std::max(hw_buffer_size,
+                             std::min(latency_hint.seconds() * hw_sample_rate,
+                                      hw_buffer_size * 4));
+      break;
+    default:
+      NOTREACHED();
+      break;
+  }
   test_runner::WebTestInterfaces* interfaces =
       LayoutTestRenderThreadObserver::GetInstance()->test_interfaces();
-  return interfaces->CreateAudioDevice(44100, 128);
+  return interfaces->CreateAudioDevice(hw_sample_rate, buffer_size);
 }
 
 WebClipboard* LayoutTestContentRendererClient::OverrideWebClipboard() {