Revert of [intrinsic] Drop the %_ValueOf intrinsic.

src/debug/mirrors.js

Index: src/debug/mirrors.js
diff --git a/src/debug/mirrors.js b/src/debug/mirrors.js
index adf5133da5e9f7961d8017f5c634f612de498659..2e7920d9b4ff4d9a27f28944f7d5d128eac8d683 100644
--- a/src/debug/mirrors.js
+++ b/src/debug/mirrors.js
@@ -19,6 +19,7 @@
 var promiseResultSymbol = utils.ImportNow("promise_result_symbol");
 var SetIteratorNext;
 var SetValues;
+var SymbolToString;
 
 utils.Import(function(from) {
   ErrorToString = from.ErrorToString;
@@ -27,6 +28,7 @@
   MapIteratorNext = from.MapIteratorNext;
   SetIteratorNext = from.SetIteratorNext;
   SetValues = from.SetValues;
+  SymbolToString = from.SymbolToString;
 });
 
 // ----------------------------------------------------------------------------
@@ -684,12 +686,12 @@
 
 
 SymbolMirror.prototype.description = function() {
-  return %SymbolDescription(%ValueOf(this.value_));
+  return %SymbolDescription(%_ValueOf(this.value_));
 }
 
 
 SymbolMirror.prototype.toText = function() {
-  return %SymbolDescriptiveString(%ValueOf(this.value_));
+  return %_Call(SymbolToString, this.value_);
 }