Setting convolver buffer needs to update number of output channels

third_party/WebKit/LayoutTests/webaudio/Convolver/convolver-response-4-chan.html

Index: third_party/WebKit/LayoutTests/webaudio/Convolver/convolver-response-4-chan.html
diff --git a/third_party/WebKit/LayoutTests/webaudio/Convolver/convolver-response-4-chan.html b/third_party/WebKit/LayoutTests/webaudio/Convolver/convolver-response-4-chan.html
index 843c81e3ca3df6d3bc13d6cf731fd12f31075602..34a0486906035cc69720b18ab4d10bf013d789f5 100644
--- a/third_party/WebKit/LayoutTests/webaudio/Convolver/convolver-response-4-chan.html
+++ b/third_party/WebKit/LayoutTests/webaudio/Convolver/convolver-response-4-chan.html
@@ -96,6 +96,51 @@
                 .then(() => task.done());
           });
 
+      audit.define(
+        {
+          label: 'delayed buffer set',
+          description: 'Delayed set of 4-channel response'
+        },
+        (task, should) => {
+          // Don't really care about the output for this test.  It's to verify
+          // we don't crash in a debug build when setting the convolver buffer
+          // after creating the graph.
+          let context = new OfflineAudioContext(1, renderFrames, sampleRate);
+          let src = new OscillatorNode(context);
+          let convolver = new ConvolverNode(context, {
+            disableNormalization: true
+          });
+          let buffer = new AudioBuffer({
+            numberOfChannels: 4,
+            length: 4,
+            sampleRate: context.sampleRate
+          });
+
+          // Impulse responses for the convolver aren't important, as long as
+          // it's not all zeroes.
+          for (let k = 0; k < buffer.numberOfChannels; ++k) {
+            buffer.getChannelData(k).fill(1);
+          }
+
+          src.connect(convolver).connect(context.destination);
+
+          // Set the buffer after a few render quanta have passed.  The actual
+          // value must be least one, but is otherwise arbitrary.
+          context.suspend(512 / context.sampleRate)
+            .then(() => convolver.buffer = buffer)
+            .then(() => context.resume());
+
+         src.start();
+         context.startRendering()
+           .then(audioBuffer => {
+             // Just make sure output is not silent.
+             should(audioBuffer.getChannelData(0),
+                 'Output with delayed setting of convolver buffer')
+               .notBeConstantValueOf(0);
+           })
+           .then(() => task.done());
+        });
+
       function fourChannelResponseTest(options, should) {
         // Create an 4-channel offline context.  The first two channels are for
         // the stereo output of the convolver and the next two channels are for