[builtins] Introduce proper Float64Atan and Float64Atan2 operators.

src/builtins.h

Index: src/builtins.h
diff --git a/src/builtins.h b/src/builtins.h
index 5a2ab29ac20ff1ad63d6d5324ff78ccbc92fe70d..d0191db83e473654aab90b685f95bc81db2585f0 100644
--- a/src/builtins.h
+++ b/src/builtins.h
@@ -131,7 +131,6 @@ inline bool operator&(BuiltinExtraArguments lhs, BuiltinExtraArguments rhs) {
                                                                \
   V(MathAcos, kNone)                                           \
   V(MathAsin, kNone)                                           \
-  V(MathAtan, kNone)                                           \
   V(MathFround, kNone)                                         \
   V(MathImul, kNone)                                           \
                                                                \
@@ -321,6 +320,8 @@ inline bool operator&(BuiltinExtraArguments lhs, BuiltinExtraArguments rhs) {
   V(GeneratorPrototypeNext, 2)        \
   V(GeneratorPrototypeReturn, 2)      \
   V(GeneratorPrototypeThrow, 2)       \
+  V(MathAtan, 2)                      \
+  V(MathAtan2, 3)                     \
   V(MathCeil, 2)                      \
   V(MathClz32, 2)                     \
   V(MathFloor, 2)                     \
@@ -615,6 +616,10 @@ class Builtins {
   static void Generate_InternalArrayCode(MacroAssembler* masm);
   static void Generate_ArrayCode(MacroAssembler* masm);
 
+  // ES6 section 20.2.2.6 Math.atan ( x )
+  static void Generate_MathAtan(CodeStubAssembler* assembler);
+  // ES6 section 20.2.2.8 Math.atan2 ( y, x )
+  static void Generate_MathAtan2(CodeStubAssembler* assembler);
   // ES6 section 20.2.2.10 Math.ceil ( x )
   static void Generate_MathCeil(CodeStubAssembler* assembler);
   // ES6 section 20.2.2.11 Math.clz32 ( x )