Add FetchDataConsumerHandle and utility functions/classes

Source/modules/fetch/CompositeDataConsumerHandle.h

 // Copyright 2015 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.
 
 #ifndef CompositeDataConsumerHandle_h
 #define CompositeDataConsumerHandle_h
 
 #include "public/platform/WebDataConsumerHandle.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
@@ skipping 11 matching lines @@
     {
         ASSERT(handle);
         return adoptPtr(new CompositeDataConsumerHandle(handle));
     }
     ~CompositeDataConsumerHandle() override;
 
     // This function should be called on the thread on which this object
     // was created. |handle| must not be null and must not be locked.
     void update(PassOwnPtr<WebDataConsumerHandle> /* handle */);
 
-    // Utility static methods each of which provides a "basic block" of
-    // a CompositeDataConsumerHandle. For example, a user can create
-    // a CompositeDataConsumerHandle with a "waiting" handle to provide
-    // WebDataConsumerHandle APIs while waiting for another handle. When that
-    // handle arrives, the user will use |update| to replace the "waiting"
-    // handle with the arrived one.
-    //
-    // Returns a handle that returns ShouldWait for read / beginRead and
-    // UnexpectedError for endRead.
-    static PassOwnPtr<WebDataConsumerHandle> createWaitingHandle();
-
-    // Returns a handle that returns Done for read / beginRead and
-    // UnexpectedError for endRead.
-    static PassOwnPtr<WebDataConsumerHandle> createDoneHandle();
-
 private:
     class Context;
     class ReaderImpl;
     Reader* obtainReaderInternal(Client*) override;
 
     explicit CompositeDataConsumerHandle(PassOwnPtr<WebDataConsumerHandle>);
 
     RefPtr<Context> m_context;
 };
 
 } // namespace blink
 
 #endif // CompositeDataConsumerHandle_h