Rewrite decodeURL as builtin function, remove now unused runtime functions.

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"
 
 namespace v8 {
 namespace internal {
 
 class Uri : public AllStatic {
  public:
+  // ES6 section 18.2.6.2 decodeURI (encodedURI)
+  static MaybeHandle<String> DecodeUri(Isolate* isolate, Handle<String> uri) {
+    return Decode(isolate, uri, true);
+  }
+
+  // ES6 section 18.2.6.3 decodeURIComponent (encodedURIComponent)
+  static MaybeHandle<String> DecodeUriComponent(Isolate* isolate,
+                                                Handle<String> component) {
+    return Decode(isolate, component, false);
+  }
+
+  // ES6 section 18.2.6.4 encodeURI (uri)
   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);
   }
 
-  // DecodeUri
-  // DecodeUriComponent
-  // escape
-  // unescape
-
  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);
-  // decode
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_URI_H_