[Fetch] Support various operations after reading data partially.

Source/modules/fetch/Body.cpp

Index: Source/modules/fetch/Body.cpp
diff --git a/Source/modules/fetch/Body.cpp b/Source/modules/fetch/Body.cpp
index 798cd4b2b7418d2e0d238896a6e5409496b3be06..6b43a22094c661901cda9335c75f4c832d802de9 100644
--- a/Source/modules/fetch/Body.cpp
+++ b/Source/modules/fetch/Body.cpp
@@ -59,7 +59,7 @@ public:
         Errored,
         BodyUsed,
     };
-    ReadableStreamSource(Body* body) : m_body(body), m_state(Initial), m_queueCount(0)
+    ReadableStreamSource(Body* body) : m_body(body), m_state(Initial)
     {
         if (m_body->buffer()) {
             m_bodyStreamBuffer = m_body->buffer();
@@ -100,13 +100,12 @@ public:
         }
     }
     // Creates a new BodyStreamBuffer to drain the data.
-    BodyStreamBuffer* createDrainingStream(bool* dataLost)
+    BodyStreamBuffer* createDrainingStream()
     {
         ASSERT(!m_drainingStreamBuffer);
         ASSERT(m_state != Initial);
         ASSERT(m_state != BodyUsed);
         ASSERT(m_stream);
-        ASSERT(dataLost);
         m_drainingStreamBuffer = new BodyStreamBuffer();
         if (m_state == Errored) {
             m_drainingStreamBuffer->error(exception());
@@ -116,7 +115,6 @@ public:
         Deque<std::pair<RefPtr<DOMArrayBuffer>, size_t>> tmp_queue;
         if (m_stream->stateInternal() == ReadableStream::Readable)
             m_stream->readInternal(tmp_queue);
-        *dataLost = m_queueCount != tmp_queue.size();
         while (!tmp_queue.isEmpty()) {
             std::pair<RefPtr<DOMArrayBuffer>, size_t> data = tmp_queue.takeFirst();
             m_drainingStreamBuffer->write(data.first);
@@ -183,12 +181,10 @@ private:
 
     void write(PassRefPtr<DOMArrayBuffer> buf)
     {
-        if (m_drainingStreamBuffer) {
+        if (m_drainingStreamBuffer)
             m_drainingStreamBuffer->write(buf);
-        } else {
-            ++m_queueCount;
+        else
             m_stream->enqueue(buf);
-        }
     }
     void close()
     {
@@ -228,8 +224,6 @@ private:
     Member<BodyStreamBuffer> m_drainingStreamBuffer;
     Member<ReadableStreamImpl<ReadableStreamChunkTypeTraits<DOMArrayBuffer>>> m_stream;
     State m_state;
-    // The count of the chunks which were enqueued to the ReadableStream.
-    size_t m_queueCount;
 };
 
 ScriptPromise Body::readAsync(ScriptState* scriptState, ResponseType type)
@@ -256,8 +250,7 @@ ScriptPromise Body::readAsync(ScriptState* scriptState, ResponseType type)
 
     if (m_stream) {
         ASSERT(m_streamSource);
-        bool dataLost;
-        m_streamSource->createDrainingStream(&dataLost)->readAllAndCreateBlobHandle(contentTypeForBuffer(), new BlobHandleReceiver(this));
+        m_streamSource->createDrainingStream()->readAllAndCreateBlobHandle(contentTypeForBuffer(), new BlobHandleReceiver(this));
     } else if (buffer()) {
         buffer()->readAllAndCreateBlobHandle(contentTypeForBuffer(), new BlobHandleReceiver(this));
     } else {
@@ -369,10 +362,10 @@ bool Body::streamAccessed() const
     return m_stream;
 }
 
-BodyStreamBuffer* Body::createDrainingStream(bool* dataLost)
+BodyStreamBuffer* Body::createDrainingStream()
 {
     ASSERT(m_stream);
-    BodyStreamBuffer* newBuffer = m_streamSource->createDrainingStream(dataLost);
+    BodyStreamBuffer* newBuffer = m_streamSource->createDrainingStream();
     m_stream = nullptr;
     m_streamSource = nullptr;
     return newBuffer;