Better handle reentrancy into DocumentLoader::dataReceived().

Source/core/loader/DocumentLoader.h

Index: Source/core/loader/DocumentLoader.h
diff --git a/Source/core/loader/DocumentLoader.h b/Source/core/loader/DocumentLoader.h
index 69a160c4a66a272a265db155e0154a06900270a1..4af2c3d0d99c85915077a9c2b0c9c4976bbe5768 100644
--- a/Source/core/loader/DocumentLoader.h
+++ b/Source/core/loader/DocumentLoader.h
@@ -45,8 +45,11 @@
 #include "platform/network/ResourceError.h"
 #include "platform/network/ResourceRequest.h"
 #include "platform/network/ResourceResponse.h"
+#include "wtf/Deque.h"
 #include "wtf/HashSet.h"
+#include "wtf/OwnPtr.h"
 #include "wtf/RefPtr.h"
+#include "wtf/Vector.h"
 
 namespace blink {
 
@@ -176,6 +179,7 @@ private:
     void updateRequest(Resource*, const ResourceRequest&) final;
     void responseReceived(Resource*, const ResourceResponse&, PassOwnPtr<WebDataConsumerHandle>) final;
     void dataReceived(Resource*, const char* data, unsigned length) final;
+    void processData(const char* data, unsigned length);
     void notifyFinished(Resource*) final;
 
     bool maybeLoadEmpty();
@@ -232,6 +236,10 @@ private:
         MainResourceDone
     };
     State m_state;
+
+    // Used to protect against reentrancy into dataReceived().
+    bool m_inDataReceived;
+    Deque<OwnPtr<Vector<char>>> m_dataQueue;

[Nate Chapin, 2015/08/05 18:27:06]

I assume the OwnPtr here is actually necessary (or at least saves a copy)?

Can/should we use SharedBuffer here for readability?

[dcheng, 2015/08/05 21:57:12]

It's to save a copy. If we could use std::move() and Deque::append() had a
move-only equivalent like std::vector::emplace_back, we wouldn't need this.

One alternative is to do:
  m_dataQueue.append(Vector());
  m_dataQueue.last().swap(buffer);
which would also avoid the copy, and allow us to simplify the type to
Deque<Vector<char>>.

Using Dequeue<RefPtr<SharedBuffer>> doesn't really seem better: the refcounting
is unnecessary.

As a final option, if it's not important to preserve the exact chunking, I can
just dump everything into a Deque<char>. This means multiple calls to
dataReceived() might get batched, but maybe it doesn't matter?

 };
 
 DECLARE_WEAK_IDENTIFIER_MAP(DocumentLoader);