Remove memory allocation in RendererWebAudioDeviceImpl::Render

Bug: 1137718
Change-Id: Ia7108d84d09bc3f48058fc15989612389abd7664
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2470567
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Auto-Submit: Olga Sharonova <olka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#818465}

content/renderer/media/renderer_webaudiodevice_impl.cc

@@ -161,6 +161,9 @@ RendererWebAudioDeviceImpl::RendererWebAudioDeviceImpl(
 
   // Specify the latency info to be passed to the browser side.
   sink_params_.set_latency_tag(latency);
+
+  web_audio_dest_data_ =
+      blink::WebVector<float*>(static_cast<size_t>(sink_params_.channels()));
 }
 
 RendererWebAudioDeviceImpl::~RendererWebAudioDeviceImpl() {
@@ -234,9 +237,9 @@ int RendererWebAudioDeviceImpl::Render(base::TimeDelta delay,
                                        int prior_frames_skipped,
                                        media::AudioBus* dest) {
   // Wrap the output pointers using WebVector.
-  WebVector<float*> web_audio_dest_data(static_cast<size_t>(dest->channels()));
+  CHECK_EQ(dest->channels(), sink_params_.channels());
   for (int i = 0; i < dest->channels(); ++i)
-    web_audio_dest_data[i] = dest->channel(i);
+    web_audio_dest_data_[i] = dest->channel(i);
 
   if (!delay.is_zero()) {  // Zero values are send at the first call.
     // Substruct the bus duration to get hardware delay.
@@ -246,7 +249,7 @@ int RendererWebAudioDeviceImpl::Render(base::TimeDelta delay,
   DCHECK_GE(delay, base::TimeDelta());
 
   client_callback_->Render(
-      web_audio_dest_data, dest->frames(), delay.InSecondsF(),
+      web_audio_dest_data_, dest->frames(), delay.InSecondsF(),
       (delay_timestamp - base::TimeTicks()).InSecondsF(), prior_frames_skipped);
 
   return dest->frames();

content/renderer/media/renderer_webaudiodevice_impl.h

@@ -19,6 +19,7 @@
 #include "third_party/blink/public/common/tokens/tokens.h"
 #include "third_party/blink/public/platform/web_audio_device.h"
 #include "third_party/blink/public/platform/web_audio_latency_hint.h"
+#include "third_party/blink/public/platform/web_vector.h"
 
 namespace base {
 class SingleThreadTaskRunner;
@@ -97,6 +98,9 @@ class CONTENT_EXPORT RendererWebAudioDeviceImpl
   // Weak reference to the callback into WebKit code.
   blink::WebAudioDevice::RenderCallback* const client_callback_;
 
+  // Used to wrap AudioBus to be passed into |client_callback_|.
+  blink::WebVector<float*> web_audio_dest_data_;
+
   // To avoid the need for locking, ensure the control methods of the
   // blink::WebAudioDevice implementation are called on the same thread.
   base::ThreadChecker thread_checker_;