Fix Active Processing Tests

The WebAudio specification states that if there are no actively
processing AudioNodes connected to an AudioWorkletNode there should
be zero channels of input:
https://webaudio.github.io/web-audio-api/#audioworkletprocess-callback-parameters

crrev.com/c/2159759 aligned Chromium's behavior to the specification,
but the WPTs were never updated.

This CL updates the WPTs to align with the current specification text.

Bug: 1073247
Change-Id: If2fac435ba99b209ed6e56e3d3413bb374606fbf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4222291
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Commit-Queue: Michael Wilson <mjwilson@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1101865}

webaudio/the-audio-api/the-audiobuffersourcenode-interface/active-processing.https.html

@@ -62,12 +62,12 @@
             .then(renderedBuffer => {
               let output = renderedBuffer.getChannelData(0);
 
-              // Find the first time the number of channels changes to 1.
-              let countChangeIndex = output.findIndex(x => x == 1);
+              // Find the first time the number of channels changes to 0.
+              let countChangeIndex = output.findIndex(x => x == 0);
 
               // Verify that the count did change.  If it didn't there's a bug
-              // in the imploementation, or it takes longer than the render
-              // length to change.  for the latter case, increase the render
+              // in the implementation, or it takes longer than the render
+              // length to change.  For the latter case, increase the render
               // length, but it can't be arbitrarily large.  The change needs to
               // happen at some reasonable time after the source stops.
               should(countChangeIndex >= 0, 'Number of channels changed')
@@ -84,11 +84,11 @@
                   .beConstantValueOf(numberOfChannels);
 
               // Verify that after the source has stopped, the number of
-              // channels is 1.
+              // channels is 0.
               should(
                   output.slice(countChangeIndex),
                   `Number of channels in input[${countChangeIndex}:]`)
-                  .beConstantValueOf(1);
+                  .beConstantValueOf(0);
             })
             .then(() => task.done());
       });

webaudio/the-audio-api/the-channelmergernode-interface/active-processing.https.html

@@ -49,8 +49,8 @@
         // Expected number of output channels from the merger node.  We should
         // start with the number of inputs, because the source (oscillator) is
         // actively processing.  When the source stops, the number of channels
-        // should change to 1.
-        const expectedValues = [numberOfInputs, 1];
+        // should change to 0.
+        const expectedValues = [numberOfInputs, 0];
         let index = 0;
 
         testerNode.port.onmessage = event => {

webaudio/the-audio-api/the-convolvernode-interface/active-processing.https.html

@@ -49,8 +49,8 @@
         // Expected number of output channels from the convolver node.  We should
         // start with the number of inputs, because the source (oscillator) is
         // actively processing.  When the source stops, the number of channels
-        // should change to 1.
-        const expectedValues = [2, 1];
+        // should change to 0.
+        const expectedValues = [2, 0];
         let index = 0;
 
         testerNode.port.onmessage = event => {