Introduce FetchFormDataConsumerHandle.

Source/modules/fetch/FetchDataConsumerHandle.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 FetchDataConsumerHandle_h
 #define FetchDataConsumerHandle_h
 
 #include "modules/ModulesExport.h"
 #include "platform/blob/BlobData.h"
+#include "platform/network/FormData.h"
 #include "public/platform/WebDataConsumerHandle.h"
 #include "wtf/Forward.h"
 #include "wtf/PassRefPtr.h"
 
 namespace blink {
 
 // This is an interface class that adds Reader's blobDataHandle() to
 // WebDataConsumerHandle.
 // This class works not very well with Oilpan: As this class is not garbage
 // collected while many clients or related objects may be, it is very easy
 // to create a reference cycle. When an client is garbage collected, making
 // the client own the handle is the right way.
 class MODULES_EXPORT FetchDataConsumerHandle : public WebDataConsumerHandle {
 public:
     class Reader : public WebDataConsumerHandle::Reader {
     public:
         enum BlobSizePolicy {
             // The returned blob must have a valid size (i.e. != kuint64max).
             DisallowBlobWithInvalidSize,
             // The returned blob can have an invalid size.
             AllowBlobWithInvalidSize
         };
 
         // Drains the data as a BlobDataHandle.
         // If this function returns non-null BlobDataHandle:
         // - The bytes that will be read from the returned BlobDataHandle
         //   must be idential to the bytes that would be read through
         //   WebDataConsumerHandle::Reader APIs without calling this function.
         // - Subsequent calls to read() / beginRead() return |Done|.

[hiroshige, 2015/08/11 09:35:01]

Please add "and subsequent calls to drainAsFormData() return nullptr.".

[yhirano, 2015/08/11 11:36:01]

I rewrote comments.

         // This function can return |nullptr|, and in such cases this
         // function is no-op.
         // This function returns |nullptr| when called during two-phase read.
         virtual PassRefPtr<BlobDataHandle> drainAsBlobDataHandle(BlobSizePolicy = DisallowBlobWithInvalidSize) { return nullptr; }
+
+        // Drains the data as a FormData.
+        // This function returns a non-null form data when
+        // - The handle is made from a FormData-convertible type,
+        // - The reader is running on a suitable thread, and

[hiroshige, 2015/08/11 09:35:01]

What is "a suitable thread"? Isn't this a general threading restriction of the
Reader thread?

[yhirano, 2015/08/11 11:36:01]

Sorry the restriction was gone.

+        // - No data is read yet.
+        // After that read() / beginRead() will return |Done|.

[hiroshige, 2015/08/11 09:35:01]

Please add "and drainAsBlobDataHandle() will return nullptr".

[yhirano, 2015/08/11 11:36:01]

I rewrote comments.

+        // Otherwise this function does nothing and returns null.
+        // This function returns |nullptr| when called during two-phase read.
+        virtual PassRefPtr<FormData> drainAsFormData() { return nullptr; }
     };
 
     // TODO(yhirano): obtainReader() is currently non-virtual override, and
     // will be changed into virtual override when we can use scoped_ptr /
     // unique_ptr in both Blink and Chromium.
     PassOwnPtr<Reader> obtainReader(Client* client) { return adoptPtr(obtainReaderInternal(client)); }
 
 private:
     Reader* obtainReaderInternal(Client*) override = 0;
 };
 
 } // namespace blink
 
 #endif // FetchDataConsumerHandle_h