Instrument AudioContext.getChannelData for identifiability study.

Bug: 973801
Change-Id: I5bc5154a5aecb85b5f04a70c238f3b7ef684b8df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354668
Commit-Queue: Russ Hamilton <behamilton@google.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798135}

third_party/blink/renderer/core/frame/dactyloscoper.cc

@@ -73,4 +73,17 @@ void Dactyloscoper::RecordDirectSurface(ExecutionContext* context,
   Dactyloscoper::RecordDirectSurface(context, feature, builder.GetToken());
 }
 
+void Dactyloscoper::RecordDirectSurface(ExecutionContext* context,
+                                        WebFeature feature,
+                                        NotShared<DOMFloat32Array> buffer) {
+  if (!IdentifiabilityStudySettings::Get()->IsActive() || !context)
+    return;
+  if (buffer.IsNull() || buffer->lengthAsSizeT() == 0)
+    return;
+  IdentifiableTokenBuilder builder(
+      base::make_span(static_cast<uint8_t*>(buffer->BaseAddress()),
+                      buffer->byteLengthAsSizeT()));
+  Dactyloscoper::RecordDirectSurface(context, feature, builder.GetToken());
+}
+
 }  // namespace blink

third_party/blink/renderer/core/frame/dactyloscoper.h

@@ -8,6 +8,8 @@
 #include "third_party/blink/public/common/privacy_budget/identifiable_token.h"
 #include "third_party/blink/renderer/core/core_export.h"
 #include "third_party/blink/renderer/core/frame/web_feature.h"
+#include "third_party/blink/renderer/core/typed_arrays/array_buffer_view_helpers.h"
+#include "third_party/blink/renderer/core/typed_arrays/dom_typed_array.h"
 #include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
 #include "third_party/blink/renderer/platform/wtf/forward.h"
 #include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
@@ -33,6 +35,9 @@ class CORE_EXPORT Dactyloscoper {
   static void RecordDirectSurface(ExecutionContext*,
                                   WebFeature,
                                   Vector<String>);
+  static void RecordDirectSurface(ExecutionContext*,
+                                  WebFeature,
+                                  NotShared<DOMFloat32Array>);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Dactyloscoper);

third_party/blink/renderer/modules/webaudio/audio_buffer.idl

@@ -37,7 +37,7 @@
 
     // Channel access
     readonly attribute unsigned long numberOfChannels;
-    [HighEntropy, Measure, RaisesException] Float32Array getChannelData(
+    [HighEntropy=Direct, Measure, RaisesException] Float32Array getChannelData(
         unsigned long channelIndex);
     [HighEntropy, Measure, RaisesException] void copyFromChannel(
         Float32Array destination,