[Fetch API] Remove DrainingBuffer.

Source/modules/fetch/FetchManager.cpp

Index: Source/modules/fetch/FetchManager.cpp
diff --git a/Source/modules/fetch/FetchManager.cpp b/Source/modules/fetch/FetchManager.cpp
index 302c0547d0905e51e0fc992fefb40a09a797703c..36040b413399870cd8e0e626a52f08084600b4f1 100644
--- a/Source/modules/fetch/FetchManager.cpp
+++ b/Source/modules/fetch/FetchManager.cpp
@@ -121,7 +121,7 @@ void FetchManager::Loader::didReceiveResponse(unsigned long, const ResourceRespo
             break;
         }
     }
-    FetchResponseData* responseData = FetchResponseData::createWithBuffer(BodyStreamBuffer::create(createFetchDataConsumerHandleFromWebHandle(handle)));
+    FetchResponseData* responseData = FetchResponseData::createWithBuffer(new BodyStreamBuffer(createFetchDataConsumerHandleFromWebHandle(handle)));
     responseData->setStatus(response.httpStatusCode());
     responseData->setStatusMessage(response.httpStatusText());
     for (auto& it : response.httpHeaderFields())
@@ -327,7 +327,9 @@ void FetchManager::Loader::performHTTPFetch(bool corsFlag, bool corsPreflightFla
 
     if (m_request->method() != "GET" && m_request->method() != "HEAD") {
         if (BodyStreamBuffer* buffer = m_request->buffer()) {
-            RefPtr<BlobDataHandle> blobDataHandle = buffer->handle()->obtainReader(nullptr)->drainAsBlobDataHandle(FetchDataConsumerHandle::Reader::AllowBlobWithInvalidSize);
+            OwnPtr<FetchDataConsumerHandle> handle = buffer->lock(executionContext());
+            RefPtr<BlobDataHandle> blobDataHandle = handle->obtainReader(nullptr)->drainAsBlobDataHandle(FetchDataConsumerHandle::Reader::AllowBlobWithInvalidSize);
+            buffer->unlock(handle.release());

[hiroshige, 2015/07/21 12:14:01]

Can we move L330-L332 to BodyStreamBuffer::drainAsBlobDataHandle()?
By doing so, we can remove all unlock() calls from outside BodyStreamBuffer and
make unlock() private.

[yhirano, 2015/07/22 09:42:45]

Done.

             RefPtr<FormData> httpBody(FormData::create());
             if (blobDataHandle)
                 httpBody->appendBlob(blobDataHandle->uuid(), blobDataHandle);