Add a default constructor for VarArrayBuffer, so that it can be used by ext::DictField.

ppapi/cpp/var_array_buffer.h

Index: ppapi/cpp/var_array_buffer.h
diff --git a/ppapi/cpp/var_array_buffer.h b/ppapi/cpp/var_array_buffer.h
index fd2b05b04cf0ed4e43cfd9d4cbdad551180e8e51..7d1f9ad48c41edba56739c9d37d2a72046cafe91 100644
--- a/ppapi/cpp/var_array_buffer.h
+++ b/ppapi/cpp/var_array_buffer.h
@@ -19,6 +19,10 @@ namespace pp {
 /// <code>HandleMessage</code> functions of <code>Instance</code>.
 class VarArrayBuffer : public Var {
  public:
+  /// The default constructor constructs a <code>VarArrayBuffer</code> which is
+  /// 0 byte long.
+  VarArrayBuffer();
+
   /// Construct a <code>VarArrayBuffer</code> given a var for which
   /// is_array_buffer() is true. This will refer to the same
   /// <code>ArrayBuffer</code> as var, but allows you to access methods
@@ -27,7 +31,7 @@ class VarArrayBuffer : public Var {
   /// @param[in] var An <code>ArrayBuffer</code> var.
   explicit VarArrayBuffer(const Var& var);
 
-  /// Construct a new <code>VarArrayBuffer_Dev</code> which is
+  /// Construct a new <code>VarArrayBuffer</code> which is
   /// <code>size_in_bytes</code> bytes long and initialized to zero.
   ///
   /// @param[in] size_in_bytes The size of the constructed
@@ -50,7 +54,7 @@ class VarArrayBuffer : public Var {
   /// This function assigns one <code>VarArrayBuffer</code> to another
   /// <code>VarArrayBuffer</code>. A Var's assignment operator is overloaded
   /// here so that we can check for assigning a non-ArrayBuffer var to a
-  /// <code>VarArrayBuffer_Dev</code>.
+  /// <code>VarArrayBuffer</code>.
   ///
   /// @param[in] other The <code>VarArrayBuffer</code> to be assigned.
   ///
@@ -90,6 +94,9 @@ class VarArrayBuffer : public Var {
   /// space. Use this if you want to save memory but might want to call Map()
   /// to map the buffer again later.
   void Unmap();
+
+ private:
+  void ConstructWithSize(uint32_t size_in_bytes);
 };
 
 }  // namespace pp