Remove unnecessary checks and runtime calls from ToLength

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index de64541496f41ac4ce59cc7836943588804a0acb..160d82cd88ab6a9682fcf416e15083611924337d 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -732,12 +732,12 @@ function ToInteger(x) {
 }
 
 
-// ES6, draft 08-24-14, section 7.1.15
+// ES6, section 7.1.15
 function ToLength(arg) {
-  arg = ToInteger(arg);
-  if (arg < 0) return 0;
-  return arg < GlobalNumber.MAX_SAFE_INTEGER ? arg
-                                             : GlobalNumber.MAX_SAFE_INTEGER;
+  arg = TO_NUMBER_INLINE(arg);

[adamk, 2015/08/24 22:42:17]

Not sure what the state of the art is...should this be "arg = +arg"? (or should
we add a TO_NUMBER macro that does +(arg)?)

+  if (arg <= 0) return 0;
+  arg = %_MathFloor(arg);
+  return arg < kMaxSafeInteger ? arg : kMaxSafeInteger;
 }