Merge math function ids and custom call generator ids.

src/math.js

Index: src/math.js
diff --git a/src/math.js b/src/math.js
index 2e886d099a9b7455a638e9787bffe79630ccae06..90667d76cf90206aaf20b87908a395d059650473 100644
--- a/src/math.js
+++ b/src/math.js
@@ -258,15 +258,6 @@ function SetupMath() {
     "max", MathMax,
     "min", MathMin
   ));
-
-  // The values here are from the MathFunctionId enum in objects.h.
-  %SetMathFunctionId($Math.floor, 1);
-  %SetMathFunctionId($Math.round, 2);
-  %SetMathFunctionId($Math.abs, 4);
-  %SetMathFunctionId($Math.sqrt, 0xd);
-  %SetMathFunctionId($Math.pow, 0xe);
-  // TODO(erikcorry): Set the id of the other functions so they can be
-  // optimized.
 };