[runtime] Use utils.InstallFunctions for Symbol.prototype[@@toPrimitive].

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1310163004

Cr-Commit-Position: refs/heads/master@{#30474}

src/symbol.js

@@ -119,13 +119,13 @@ utils.InstallFunctions(GlobalSymbol, DONT_ENUM, [
 
 %AddNamedProperty(
     GlobalSymbol.prototype, "constructor", GlobalSymbol, DONT_ENUM);
-utils.SetFunctionName(SymbolToPrimitive, toPrimitiveSymbol);
-%AddNamedProperty(
-    GlobalSymbol.prototype, toPrimitiveSymbol, SymbolToPrimitive,
-    DONT_ENUM | READ_ONLY);
 %AddNamedProperty(
     GlobalSymbol.prototype, toStringTagSymbol, "Symbol", DONT_ENUM | READ_ONLY);
 
+utils.InstallFunctions(GlobalSymbol.prototype, DONT_ENUM | READ_ONLY, [
+  toPrimitiveSymbol, SymbolToPrimitive
+]);
+
 utils.InstallFunctions(GlobalSymbol.prototype, DONT_ENUM, [
   "toString", SymbolToString,
   "valueOf", SymbolValueOf