[wrapper-tracing] Untangle non-trivial mixin ctors

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/fetch/BodyStreamBuffer.h"
 
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/V8HiddenValue.h"
 #include "bindings/core/v8/V8ThrowException.h"
 #include "core/dom/DOMArrayBuffer.h"
@@ skipping 57 matching lines @@
     FetchDataLoader::Client::trace(visitor);
   }
 
  private:
   void contextDestroyed() override { m_buffer->stopLoading(); }
 
   Member<BodyStreamBuffer> m_buffer;
   Member<FetchDataLoader::Client> m_client;
 };
 
+BodyStreamBuffer* BodyStreamBuffer::create(ScriptState* scriptState,
+                                           BytesConsumer* consumer) {
+  BodyStreamBuffer* buffer = new BodyStreamBuffer(scriptState, consumer);
+
+  ScriptValue readableStream = ReadableStreamOperations::createReadableStream(
+      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());
+
+  buffer->announceClientToConsumer();
+  return buffer;
+}
+
+BodyStreamBuffer* BodyStreamBuffer::create(ScriptState* scriptState,
+                                           ScriptValue stream) {
+  DCHECK(ReadableStreamOperations::isReadableStream(scriptState, stream));
+
+  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) {
-  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>();
-
-  ScriptValue readableStream = ReadableStreamOperations::createReadableStream(
-      scriptState, this,
-      ReadableStreamOperations::createCountQueuingStrategy(scriptState, 0));
-  DCHECK(!readableStream.isEmpty());
-  V8HiddenValue::setHiddenValue(
-      scriptState, body,
-      V8HiddenValue::internalBodyStream(scriptState->isolate()),
-      readableStream.v8Value());
-  m_consumer->setClient(this);
-  onStateChange();
-}
+      m_madeFromReadableStream(false) {}
 
 BodyStreamBuffer::BodyStreamBuffer(ScriptState* scriptState, ScriptValue stream)
     : UnderlyingSourceBase(scriptState),
       m_scriptState(scriptState),
-      m_madeFromReadableStream(true) {
-  DCHECK(ReadableStreamOperations::isReadableStream(scriptState, stream));
-  v8::Local<v8::Value> bodyValue = toV8(this, 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());
-}
+      m_madeFromReadableStream(true) {}
 
 ScriptValue BodyStreamBuffer::stream() {
   ScriptState::Scope scope(m_scriptState.get());
   v8::Local<v8::Value> bodyValue = toV8(this, m_scriptState.get());
   DCHECK(!bodyValue.IsEmpty());
   DCHECK(bodyValue->IsObject());
   v8::Local<v8::Object> body = bodyValue.As<v8::Object>();
   return ScriptValue(
       m_scriptState.get(),
       V8HiddenValue::getHiddenValue(
@@ skipping 51 matching lines @@
                            BodyStreamBuffer** branch2) {
   DCHECK(!isStreamLocked());
   DCHECK(!isStreamDisturbed());
   *branch1 = nullptr;
   *branch2 = nullptr;
 
   if (m_madeFromReadableStream) {
     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) {
   ASSERT(scriptState == m_scriptState.get());
   if (m_streamNeedsMore)
     return ScriptPromise::castUndefined(scriptState);
   m_streamNeedsMore = true;
   processData();
   return ScriptPromise::castUndefined(scriptState);
 }
@@ skipping 177 matching lines @@
   }
   if (isErrored)
     return BytesConsumer::createErrored(BytesConsumer::Error("error"));
 
   DCHECK(consumer);
   consumer->clearClient();
   return consumer;
 }
 
 }  // namespace blink