Remove redundant reading and writing of data about SharedBuffer.

third_party/WebKit/Source/platform/image-decoders/SegmentReader.h

 // Copyright 2016 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 SegmentReader_h
 #define SegmentReader_h
 
 #include "platform/SharedBuffer.h"
+#include "platform/SharedBufferStep.h"
 #include "platform/wtf/Noncopyable.h"
 #include "platform/wtf/PassRefPtr.h"
 #include "platform/wtf/ThreadSafeRefCounted.h"
 #include "third_party/skia/include/core/SkData.h"
 #include "third_party/skia/include/core/SkRWBuffer.h"
 #include "third_party/skia/include/core/SkRefCnt.h"
 
 namespace blink {
 
 // Interface that looks like SharedBuffer. Used by ImageDecoders to use various
@@ skipping 11 matching lines @@
     : public ThreadSafeRefCounted<SegmentReader> {
   WTF_MAKE_NONCOPYABLE(SegmentReader);
 
  public:
   // This version is thread-safe so long as no thread is modifying the
   // underlying SharedBuffer. This class does not modify it, so that would
   // mean modifying it in another way.
   static PassRefPtr<SegmentReader> CreateFromSharedBuffer(
       PassRefPtr<SharedBuffer>);
 
+  static PassRefPtr<SegmentReader> CreateFromSharedBufferStep(
+      PassRefPtr<SharedBufferStep>);
+
   // These versions use thread-safe input, so they are always thread-safe.
   static PassRefPtr<SegmentReader> CreateFromSkData(sk_sp<SkData>);
   static PassRefPtr<SegmentReader> CreateFromSkROBuffer(sk_sp<SkROBuffer>);
 
   SegmentReader() {}
   virtual ~SegmentReader() {}
   virtual size_t size() const = 0;
   virtual size_t GetSomeData(const char*& data, size_t position) const = 0;
   virtual sk_sp<SkData> GetAsSkData() const = 0;
 };
 
 }  // namespace blink
 #endif  // SegmentReader_h