[wrapper-tracing] Untangle non-trivial mixin ctors

third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.h

Index: third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.h
diff --git a/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.h b/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.h
index 78dab54d72d0e8fc16a87edbcfda1ee265f7d01e..ed49ae8774a13be289569cd24eb921f13dca3db2 100644
--- a/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.h
+++ b/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.h
@@ -29,10 +29,10 @@ class MODULES_EXPORT BodyStreamBuffer final : public UnderlyingSourceBase,
  public:
   // |consumer| must not have a client.
   // This function must be called with entering an appropriate V8 context.
-  BodyStreamBuffer(ScriptState*, BytesConsumer* /* consumer */);
+  static BodyStreamBuffer* create(ScriptState*, BytesConsumer* /* consumer */);
   // |ReadableStreamOperations::isReadableStream(stream)| must hold.
   // This function must be called with entering an appropriate V8 context.
-  BodyStreamBuffer(ScriptState*, ScriptValue stream);
+  static BodyStreamBuffer* create(ScriptState*, ScriptValue stream);
 
   ScriptValue stream();
 
@@ -69,6 +69,11 @@ class MODULES_EXPORT BodyStreamBuffer final : public UnderlyingSourceBase,
  private:
   class LoaderClient;
 
+  BodyStreamBuffer(ScriptState*, BytesConsumer* /* consumer */);
+  BodyStreamBuffer(ScriptState*, ScriptValue stream);
+
+  void announceClientToConsumer();
+
   BytesConsumer* releaseHandle();
   void close();
   void error();