Add {Map,Set}::FromArray to the API

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 00bc3364bb8edbaef662039533c5432c52e6ba56..a7390555d565fe683d5d9001a90cb25b0c05c7f9 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -2976,10 +2976,18 @@ class V8_EXPORT Map : public Object {
   Local<Array> AsArray() const;
 
   /**
-   * Creates a new Map.
+   * Creates a new empty Map.
    */
   static Local<Map> New(Isolate* isolate);
 
+  /**
+   * Creates a new Map containing the elements of array, which must be comprised
+   * of [key, value] arrays.
+   * Guaranteed to be side-effect free if the array contains no holes.

[arv (Not doing code reviews), 2015/05/26 16:37:40]

If the main use case is structured clone we could do an array where the keys and
values are interleaved.

[k0, v0, k1, v1, ... kn, vn]

[adamk, 2015/05/26 17:27:44]

Let's leave this for a later round where we optimize the performance. For now
I'd rather leave this symmetric with AsArray().

+   */
+  static V8_WARN_UNUSED_RESULT MaybeLocal<Map> FromArray(Local<Context> context,
+                                                         Local<Array> array);
+
   V8_INLINE static Map* Cast(Value* obj);
 
  private:
@@ -3001,10 +3009,17 @@ class V8_EXPORT Set : public Object {
   Local<Array> AsArray() const;
 
   /**
-   * Creates a new Set.
+   * Creates a new empty Set.
    */
   static Local<Set> New(Isolate* isolate);
 
+  /**
+   * Creates a new Set containing the items in array.
+   * Guaranteed to be side-effect free if the array contains no holes.
+   */
+  static V8_WARN_UNUSED_RESULT MaybeLocal<Set> FromArray(Local<Context> context,
+                                                         Local<Array> array);
+
   V8_INLINE static Set* Cast(Value* obj);
 
  private: