[builtins] Migrate escape/unescape from uri.js to C++.

src/uri.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_URI_H_
 #define V8_URI_H_
 
 #include "src/allocation.h"
 #include "src/objects.h"
 
@@ skipping 17 matching lines @@
   static MaybeHandle<String> EncodeUri(Isolate* isolate, Handle<String> uri) {
     return Encode(isolate, uri, true);
   }
 
   // ES6 section 18.2.6.5 encodeURIComponenet (uriComponent)
   static MaybeHandle<String> EncodeUriComponent(Isolate* isolate,
                                                 Handle<String> component) {
     return Encode(isolate, component, false);
   }
 
+  // ES6 section B.2.1.1 escape (string)
+  static MaybeHandle<String> Escape(Isolate* isolate, Handle<String> string);
+
+  // ES6 section B.2.1.2 unescape (string)
+  static MaybeHandle<String> Unescape(Isolate* isolate, Handle<String> string);
+
  private:
   static MaybeHandle<String> Decode(Isolate* isolate, Handle<String> uri,
                                     bool is_uri);
   static MaybeHandle<String> Encode(Isolate* isolate, Handle<String> uri,
                                     bool is_uri);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_URI_H_