Remove redundant reading and writing of data about SharedBuffer.

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

 // 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.
 
 #include "platform/image-decoders/SegmentReader.h"
 
 #include "platform/SharedBuffer.h"
+#include "platform/SharedBufferStep.h"
 #include "platform/wtf/Assertions.h"
 #include "platform/wtf/Noncopyable.h"
 #include "platform/wtf/PassRefPtr.h"
 #include "platform/wtf/RefPtr.h"
 #include "platform/wtf/ThreadingPrimitives.h"
 #include "third_party/skia/include/core/SkData.h"
 
 namespace blink {
 
 // SharedBufferSegmentReader ---------------------------------------------------
@@ skipping 22 matching lines @@
 
 size_t SharedBufferSegmentReader::GetSomeData(const char*& data,
                                               size_t position) const {
   return shared_buffer_->GetSomeData(data, position);
 }
 
 sk_sp<SkData> SharedBufferSegmentReader::GetAsSkData() const {
   return shared_buffer_->GetAsSkData();
 }
 
+// SharedBufferStepSegmentReader
+// ---------------------------------------------------
+
+// Interface for ImageDecoder to read a SharedBufferStep.
+class SharedBufferStepSegmentReader final : public SegmentReader {
+  WTF_MAKE_NONCOPYABLE(SharedBufferStepSegmentReader);
+
+ public:
+  SharedBufferStepSegmentReader(PassRefPtr<SharedBufferStep>);
+  size_t size() const override;
+  size_t GetSomeData(const char*& data, size_t position) const override;
+  sk_sp<SkData> GetAsSkData() const override;
+
+ private:
+  RefPtr<SharedBufferStep> step_;
+  size_t size_;
+};
+
+SharedBufferStepSegmentReader::SharedBufferStepSegmentReader(
+    PassRefPtr<SharedBufferStep> step)
+    : step_(std::move(step)), size_(step_->size()) {}
+
+size_t SharedBufferStepSegmentReader::size() const {
+  return size_;
+}
+
+size_t SharedBufferStepSegmentReader::GetSomeData(const char*& data,
+                                                  size_t position) const {
+  return step_->GetSomeData(data, position);
+}
+
+sk_sp<SkData> SharedBufferStepSegmentReader::GetAsSkData() const {
+  return step_->GetAsSkData();
+}
+
 // DataSegmentReader -----------------------------------------------------------
 
 // Interface for ImageDecoder to read an SkData.
 class DataSegmentReader final : public SegmentReader {
   WTF_MAKE_NONCOPYABLE(DataSegmentReader);
 
  public:
   DataSegmentReader(sk_sp<SkData>);
   size_t size() const override;
   size_t GetSomeData(const char*& data, size_t position) const override;
@@ skipping 123 matching lines @@
 
 PassRefPtr<SegmentReader> SegmentReader::CreateFromSharedBuffer(
     PassRefPtr<SharedBuffer> buffer) {
   return AdoptRef(new SharedBufferSegmentReader(std::move(buffer)));
 }
 
 PassRefPtr<SegmentReader> SegmentReader::CreateFromSkData(sk_sp<SkData> data) {
   return AdoptRef(new DataSegmentReader(std::move(data)));
 }
 
+PassRefPtr<SegmentReader> SegmentReader::CreateFromSharedBufferStep(
+    PassRefPtr<SharedBufferStep> step) {
+  return AdoptRef(new SharedBufferStepSegmentReader(std::move(step)));
+}
+
 PassRefPtr<SegmentReader> SegmentReader::CreateFromSkROBuffer(
     sk_sp<SkROBuffer> buffer) {
   return AdoptRef(new ROBufferSegmentReader(std::move(buffer)));
 }
 
 }  // namespace blink