Add a ref-counted data holder to ArrayBufferContents

Source/wtf/ArrayBuffer.h

Index: Source/wtf/ArrayBuffer.h
diff --git a/Source/wtf/ArrayBuffer.h b/Source/wtf/ArrayBuffer.h
index e8a737c8fcd3680cd6f5945a17a28713de15060a..a85d9e41a8afd3ffa40912ba5d56f2b4a68d7f53 100644
--- a/Source/wtf/ArrayBuffer.h
+++ b/Source/wtf/ArrayBuffer.h
@@ -50,6 +50,9 @@ public:
     // (through DOMArrayBuffer::createUninitialized).
     static inline PassRefPtr<ArrayBuffer> createUninitialized(unsigned numElements, unsigned elementByteSize);
 
+    static inline PassRefPtr<ArrayBuffer> createShared(unsigned numElements, unsigned elementByteSize);
+    static inline PassRefPtr<ArrayBuffer> createShared(const void* source, unsigned byteLength);
+
     inline void* data();
     inline const void* data() const;
     inline unsigned byteLength() const;
@@ -63,7 +66,9 @@ public:
     void removeView(ArrayBufferView*);
 
     bool transfer(ArrayBufferContents&);
-    bool isNeutered() { return m_isNeutered; }
+    bool shareContentsWith(ArrayBufferContents&);
+    bool isNeutered() const { return m_isNeutered; }
+    bool isShared() const { return m_contents.isShared(); }
 
     ~ArrayBuffer() { }
 
@@ -73,6 +78,7 @@ protected:
 private:
     static inline PassRefPtr<ArrayBuffer> create(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy);
     static inline PassRefPtr<ArrayBuffer> createOrNull(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy);
+    static inline PassRefPtr<ArrayBuffer> createShared(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy);
 
     inline PassRefPtr<ArrayBuffer> sliceImpl(unsigned begin, unsigned end) const;
     inline unsigned clampIndex(int index) const;
@@ -100,12 +106,14 @@ PassRefPtr<ArrayBuffer> ArrayBuffer::create(unsigned numElements, unsigned eleme
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(ArrayBuffer* other)
 {
+    // TODO(binji): support creating a SharedArrayBuffer by copying another ArrayBuffer?
+    ASSERT(!other->isShared());
     return ArrayBuffer::create(other->data(), other->byteLength());
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(const void* source, unsigned byteLength)
 {
-    ArrayBufferContents contents(byteLength, 1, ArrayBufferContents::ZeroInitialize);
+    ArrayBufferContents contents(byteLength, 1, ArrayBufferContents::NotShared, ArrayBufferContents::ZeroInitialize);
     RELEASE_ASSERT(contents.data());
     RefPtr<ArrayBuffer> buffer = adoptRef(new ArrayBuffer(contents));
     memcpy(buffer->data(), source, byteLength);
@@ -129,19 +137,40 @@ PassRefPtr<ArrayBuffer> ArrayBuffer::createUninitialized(unsigned numElements, u
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::create(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy policy)
 {
-    ArrayBufferContents contents(numElements, elementByteSize, policy);
+    ArrayBufferContents contents(numElements, elementByteSize, ArrayBufferContents::NotShared, policy);
     RELEASE_ASSERT(contents.data());
     return adoptRef(new ArrayBuffer(contents));
 }
 
 PassRefPtr<ArrayBuffer> ArrayBuffer::createOrNull(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy policy)
 {
-    ArrayBufferContents contents(numElements, elementByteSize, policy);
+    ArrayBufferContents contents(numElements, elementByteSize, ArrayBufferContents::NotShared, policy);
     if (!contents.data())
         return nullptr;
     return adoptRef(new ArrayBuffer(contents));
 }
 
+PassRefPtr<ArrayBuffer> ArrayBuffer::createShared(unsigned numElements, unsigned elementByteSize)
+{
+    return createShared(numElements, elementByteSize, ArrayBufferContents::ZeroInitialize);
+}
+
+PassRefPtr<ArrayBuffer> ArrayBuffer::createShared(const void* source, unsigned byteLength)
+{
+    ArrayBufferContents contents(byteLength, 1, ArrayBufferContents::Shared, ArrayBufferContents::ZeroInitialize);
+    RELEASE_ASSERT(contents.data());
+    RefPtr<ArrayBuffer> buffer = adoptRef(new ArrayBuffer(contents));
+    memcpy(buffer->data(), source, byteLength);
+    return buffer.release();
+}
+
+PassRefPtr<ArrayBuffer> ArrayBuffer::createShared(unsigned numElements, unsigned elementByteSize, ArrayBufferContents::InitializationPolicy policy)
+{
+    ArrayBufferContents contents(numElements, elementByteSize, ArrayBufferContents::Shared, policy);
+    RELEASE_ASSERT(contents.data());
+    return adoptRef(new ArrayBuffer(contents));
+}
+
 ArrayBuffer::ArrayBuffer(ArrayBufferContents& contents)
     : m_firstView(0), m_isNeutered(false)
 {