Small API improvements:

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index e8b19ec635a6b639afd57cc5ba0ed130aad6b090..0992f0bfc8199d765d8a1ca2702bb9bf4f8bac45 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -261,6 +261,10 @@ template <class T> class V8EXPORT_INLINE Handle {
     return Handle<T>(T::Cast(*that));
   }
 
+  template <class S> inline Handle<S> As() {
+    return Handle<S>::Cast(*this);
+  }
+
  private:
   T* val_;
 };
@@ -295,6 +299,10 @@ template <class T> class V8EXPORT_INLINE Local : public Handle<T> {
     return Local<T>(T::Cast(*that));
   }
 
+  template <class S> inline Local<S> As() {
+    return Local<S>::Cast(*this);
+  }
+
   /** Create a local handle for the content of another handle.
    *  The referee is kept alive by the local handle even when
    *  the original handle is destroyed/disposed.
@@ -368,6 +376,10 @@ template <class T> class V8EXPORT_INLINE Persistent : public Handle<T> {
     return Persistent<T>(T::Cast(*that));
   }
 
+  template <class S> inline Persistent<S> As() {
+    return Persistent<S>::Cast(*this);
+  }
+
   /**
    * Creates a new persistent handle for an existing local or
    * persistent handle.
@@ -1178,6 +1190,9 @@ class V8EXPORT Object : public Value {
            Handle<Value> value,
            PropertyAttribute attribs = None);
 
+  bool Set(uint32_t index,
+           Handle<Value> value);
+
   // Sets a local property on this object bypassing interceptors and
   // overriding accessors or read-only properties.
   //
@@ -1192,6 +1207,8 @@ class V8EXPORT Object : public Value {
 
   Local<Value> Get(Handle<Value> key);
 
+  Local<Value> Get(uint32_t index);
+
   // TODO(1245389): Replace the type-specific versions of these
   // functions with generic ones that accept a Handle<Value> key.
   bool Has(Handle<String> key);