ConvolverOptions.buffer should be nullable

third_party/WebKit/Source/modules/webaudio/ConvolverOptions.idl

Index: third_party/WebKit/Source/modules/webaudio/ConvolverOptions.idl
diff --git a/third_party/WebKit/Source/modules/webaudio/ConvolverOptions.idl b/third_party/WebKit/Source/modules/webaudio/ConvolverOptions.idl
index cf2b8892ef9c26e700e83a4768e09b607f90f835..4db8a8694e2b6e16a19afba3ede4b93f7cecbe7d 100644
--- a/third_party/WebKit/Source/modules/webaudio/ConvolverOptions.idl
+++ b/third_party/WebKit/Source/modules/webaudio/ConvolverOptions.idl
@@ -4,6 +4,6 @@
 
 // See https://webaudio.github.io/web-audio-api/#convolveroptions
 dictionary ConvolverOptions : AudioNodeOptions {
-    AudioBuffer buffer;
+    AudioBuffer? buffer;
     boolean disableNormalization = false;
-};
+};