[wrapper-tracing] Untangle non-trivial mixin ctors

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

Index: third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.cpp
diff --git a/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.cpp b/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.cpp
index bd4a4dfcfa9dc8c685128bd2574425beb071c3de..33879f9c3461e3a5bff5f2557e00be1713209435 100644
--- a/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.cpp
+++ b/third_party/WebKit/Source/modules/fetch/BodyStreamBuffer.cpp
@@ -75,45 +75,62 @@ class BodyStreamBuffer::LoaderClient final
   Member<FetchDataLoader::Client> m_client;
 };
 
-BodyStreamBuffer::BodyStreamBuffer(ScriptState* scriptState,
-                                   BytesConsumer* consumer)
-    : UnderlyingSourceBase(scriptState),
-      m_scriptState(scriptState),
-      m_consumer(consumer),
-      m_madeFromReadableStream(false) {
-  v8::Local<v8::Value> bodyValue = toV8(this, scriptState);

[haraken, 2016/11/24 23:36:32]

Why do we need to move the contents of the constructor to ::create?

BodyStreamBuffer::BodyStreamBuffer()
  : ... {  // <--- Object construction is complete at this point.
  ...;  // <-- So it's fine to call V8 APIs here.
}

[Michael Lippautz, 2016/11/25 07:21:26]

Thanks for the clarification, makes sense.

-  DCHECK(!bodyValue.IsEmpty());
-  DCHECK(bodyValue->IsObject());
-  v8::Local<v8::Object> body = bodyValue.As<v8::Object>();
+BodyStreamBuffer* BodyStreamBuffer::create(ScriptState* scriptState,
+                                           BytesConsumer* consumer) {
+  BodyStreamBuffer* buffer = new BodyStreamBuffer(scriptState, consumer);
 
   ScriptValue readableStream = ReadableStreamOperations::createReadableStream(
-      scriptState, this,
+      scriptState, buffer,
       ReadableStreamOperations::createCountQueuingStrategy(scriptState, 0));
   DCHECK(!readableStream.isEmpty());
+
+  v8::Local<v8::Value> bodyValue = toV8(buffer, scriptState);
+  DCHECK(!bodyValue.IsEmpty());
+  DCHECK(bodyValue->IsObject());
+  v8::Local<v8::Object> body = bodyValue.As<v8::Object>();
   V8HiddenValue::setHiddenValue(
       scriptState, body,
       V8HiddenValue::internalBodyStream(scriptState->isolate()),
       readableStream.v8Value());
-  m_consumer->setClient(this);
-  onStateChange();
+
+  buffer->announceClientToConsumer();
+  return buffer;
 }
 
-BodyStreamBuffer::BodyStreamBuffer(ScriptState* scriptState, ScriptValue stream)
-    : UnderlyingSourceBase(scriptState),
-      m_scriptState(scriptState),
-      m_madeFromReadableStream(true) {
+BodyStreamBuffer* BodyStreamBuffer::create(ScriptState* scriptState,
+                                           ScriptValue stream) {
   DCHECK(ReadableStreamOperations::isReadableStream(scriptState, stream));
-  v8::Local<v8::Value> bodyValue = toV8(this, scriptState);
+
+  BodyStreamBuffer* buffer = new BodyStreamBuffer(scriptState, stream);
+
+  v8::Local<v8::Value> bodyValue = toV8(buffer, scriptState);
   DCHECK(!bodyValue.IsEmpty());
   DCHECK(bodyValue->IsObject());
   v8::Local<v8::Object> body = bodyValue.As<v8::Object>();
-
   V8HiddenValue::setHiddenValue(
       scriptState, body,
       V8HiddenValue::internalBodyStream(scriptState->isolate()),
       stream.v8Value());
+  return buffer;
 }
 
+void BodyStreamBuffer::announceClientToConsumer() {
+  m_consumer->setClient(this);
+  onStateChange();
+}
+
+BodyStreamBuffer::BodyStreamBuffer(ScriptState* scriptState,
+                                   BytesConsumer* consumer)
+    : UnderlyingSourceBase(scriptState),
+      m_scriptState(scriptState),
+      m_consumer(consumer),
+      m_madeFromReadableStream(false) {}
+
+BodyStreamBuffer::BodyStreamBuffer(ScriptState* scriptState, ScriptValue stream)
+    : UnderlyingSourceBase(scriptState),
+      m_scriptState(scriptState),
+      m_madeFromReadableStream(true) {}
+
 ScriptValue BodyStreamBuffer::stream() {
   ScriptState::Scope scope(m_scriptState.get());
   v8::Local<v8::Value> bodyValue = toV8(this, m_scriptState.get());
@@ -184,16 +201,16 @@ void BodyStreamBuffer::tee(BodyStreamBuffer** branch1,
     ScriptValue stream1, stream2;
     ReadableStreamOperations::tee(m_scriptState.get(), stream(), &stream1,
                                   &stream2);
-    *branch1 = new BodyStreamBuffer(m_scriptState.get(), stream1);
-    *branch2 = new BodyStreamBuffer(m_scriptState.get(), stream2);
+    *branch1 = BodyStreamBuffer::create(m_scriptState.get(), stream1);
+    *branch2 = BodyStreamBuffer::create(m_scriptState.get(), stream2);
     return;
   }
   BytesConsumer* dest1 = nullptr;
   BytesConsumer* dest2 = nullptr;
   BytesConsumer::tee(m_scriptState->getExecutionContext(), releaseHandle(),
                      &dest1, &dest2);
-  *branch1 = new BodyStreamBuffer(m_scriptState.get(), dest1);
-  *branch2 = new BodyStreamBuffer(m_scriptState.get(), dest2);
+  *branch1 = BodyStreamBuffer::create(m_scriptState.get(), dest1);
+  *branch2 = BodyStreamBuffer::create(m_scriptState.get(), dest2);
 }
 
 ScriptPromise BodyStreamBuffer::pull(ScriptState* scriptState) {