WIP: Create a public v8::DictionarySchema API for bulk reads from dict objects.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index d7b7205ef0a0b18e341343875f614ca18fed6610..5f0d367e6b6aaab723fef16197e13ba6875e1970 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -302,6 +302,7 @@ class Local {
   template<class F1, class F2> friend class PersistentValueVector;
   template <class F>
   friend class ReturnValue;
+  friend class DictionarySchema;
 
   explicit V8_INLINE Local(T* that) : val_(that) {}
   V8_INLINE static Local<T> New(Isolate* isolate, T* that);
@@ -5581,6 +5582,38 @@ class V8_EXPORT AccessorSignature : public Data {
   AccessorSignature();
 };
 
+// --- Dictionary schema ---
+
+/*
+ * A DictionarySchema defines the keys expected to be present on a dictionary
+ * object and provides an efficient way of reading them.
+ */
+class V8_EXPORT DictionarySchema : public Data {
+ public:
+  static Local<DictionarySchema> New(Isolate* isolate, Local<Value> keys[],
+                                     int keyCount);
+
+  enum ValueFilter {
+    kValueFilterNone = 0,
+    kValueFilterPrimitives = 1 << 0,
+    kValueFilterObjects = 1 << 1,
+  };
+
+  /*
+   * Reads keys from the object according to the schema, in order.
+   * Reading will abort if:
+   * - an exception is thrown (Nothing<bool>() is returned)
+   * - an object that doesn't match |continue_filter| is reached
+   *   (Just(false) is returned)
+   * - all properties are read (Just(true) is returned)
+   *
+   * |index| will be updated to point to the next index left to be read;
+   * this makes repeated invocations convenient.
+   */
+  Maybe<bool> Get(Local<Context> context, Local<Object> object,
+                  ValueFilter continue_filter, Local<Value>* out_values,
+                  int out_length, int* index);
+};
 
 // --- Extensions ---