Adds support for ArrayBufferContents with external buffer.

third_party/WebKit/Source/wtf/typed_arrays/ArrayBufferContents.h

Index: third_party/WebKit/Source/wtf/typed_arrays/ArrayBufferContents.h
diff --git a/third_party/WebKit/Source/wtf/typed_arrays/ArrayBufferContents.h b/third_party/WebKit/Source/wtf/typed_arrays/ArrayBufferContents.h
index 6c5b54af6ccaca9b1ed15abfbb3f9af9c06074a9..1e125030dff11d6ddd40c4d8b35b7441a21277ae 100644
--- a/third_party/WebKit/Source/wtf/typed_arrays/ArrayBufferContents.h
+++ b/third_party/WebKit/Source/wtf/typed_arrays/ArrayBufferContents.h
@@ -43,6 +43,8 @@ class WTF_EXPORT ArrayBufferContents {
 
  public:
   using AdjustAmountOfExternalAllocatedMemoryFunction = void (*)(int64_t diff);
+  using DataDeleter = void (*)(void* data);
+  using ScopedData = std::unique_ptr<void, DataDeleter>;

[jbroman, 2017/02/28 20:01:19]

A brief comment about the expected usage of this (namely, that most callers will
want to provide WTF::ArrayBufferContents::freeMemory as the deleter) would be
useful.

[alokp, 2017/02/28 20:56:08]

Done.

 
   enum InitializationPolicy { ZeroInitialize, DontInitialize };
 
@@ -56,13 +58,7 @@ class WTF_EXPORT ArrayBufferContents {
                       unsigned elementByteSize,
                       SharingType isShared,
                       InitializationPolicy);
-
-  // Use with care. data must be allocated with allocateMemory.
-  // ArrayBufferContents will take ownership of the data and free it (using
-  // freeMemory) upon destruction.
-  // This constructor will not call observer->StartObserving(), so it is a
-  // responsibility of the caller to make sure JS knows about external memory.
-  ArrayBufferContents(void* data, unsigned sizeInBytes, SharingType isShared);
+  ArrayBufferContents(ScopedData, unsigned sizeInBytes, SharingType isShared);
 
   ~ArrayBufferContents();
 
@@ -88,9 +84,9 @@ class WTF_EXPORT ArrayBufferContents {
   void shareWith(ArrayBufferContents& other);
   void copyTo(ArrayBufferContents& other);
 
-  static void allocateMemory(size_t, InitializationPolicy, void*&);
-  static void allocateMemoryOrNull(size_t, InitializationPolicy, void*&);
-  static void freeMemory(void*, size_t);
+  static void* allocateMemory(size_t, InitializationPolicy);

[jbroman, 2017/02/28 20:01:19]

Possible bikeshed: but for most callers it might actually be nice this returned
a ScopedData with the right deleter. The couple users that don't could always
use ScopedData::release to get the raw void* out anyhow, and it would make this
less error-prone for callers other than V8.

[alokp, 2017/02/28 20:56:08]

Good idea. Although it would be a bit weird to not expose allocateMemory but
still expose freeMemory (which would be needed by V8Initializer). So I create a
helper createData function instead. I was also able to get rid of allocateMemory
since all usage has been replaced by createData.

+  static void* allocateMemoryOrNull(size_t, InitializationPolicy);
+  static void freeMemory(void*);
   static void initialize(
       AdjustAmountOfExternalAllocatedMemoryFunction function) {
     DCHECK(isMainThread());
@@ -100,10 +96,7 @@ class WTF_EXPORT ArrayBufferContents {
   }
 
  private:
-  static void allocateMemoryWithFlags(size_t,
-                                      InitializationPolicy,
-                                      int,
-                                      void*&);
+  static void* allocateMemoryWithFlags(size_t, InitializationPolicy, int);
 
   static void defaultAdjustAmountOfExternalAllocatedMemoryFunction(
       int64_t diff);
@@ -118,11 +111,11 @@ class WTF_EXPORT ArrayBufferContents {
     void allocateNew(unsigned sizeInBytes,
                      SharingType isShared,
                      InitializationPolicy);
-    void adopt(void* data, unsigned sizeInBytes, SharingType isShared);
+    void adopt(ScopedData, unsigned sizeInBytes, SharingType isShared);
     void copyMemoryFrom(const DataHolder& source);
 
-    const void* data() const { return m_data; }
-    void* data() { return m_data; }
+    const void* data() const { return m_data.get(); }
+    void* data() { return m_data.get(); }
     unsigned sizeInBytes() const { return m_sizeInBytes; }
     bool isShared() const { return m_isShared == Shared; }
 
@@ -150,7 +143,7 @@ class WTF_EXPORT ArrayBufferContents {
 #endif
     }
 
-    void* m_data;
+    ScopedData m_data;
     unsigned m_sizeInBytes;
     SharingType m_isShared;
   };