buffer,util: refactor for performance

internal/util.js definied toInteger() and toLength() but they were only
used by buffer.js. Inlining these small functions results in a small but
statistically-significant performance gain.

lib/buffer.js

@@ -254,7 +254,9 @@ function fromArrayLike(obj) {
 }
 
 function fromArrayBuffer(obj, byteOffset, length) {
-  byteOffset = internalUtil.toInteger(byteOffset);
+  // convert byteOffset to integer
+  byteOffset = +byteOffset;
+  byteOffset = byteOffset ? Math.trunc(byteOffset) : 0;
 
   const maxLength = obj.byteLength - byteOffset;
 
@@ -264,7 +266,11 @@ function fromArrayBuffer(obj, byteOffset, length) {
   if (length === undefined) {
     length = maxLength;
   } else {
-    length = internalUtil.toLength(length);
+    // convert length to non-negative integer
+    length = +length;
+    length = length ? Math.trunc(length) : 0;
+    length = length <= 0 ? 0 : Math.min(length, Number.MAX_SAFE_INTEGER);
+
     if (length > maxLength)
       throw new RangeError("'length' is out of bounds");
   }

lib/internal/util.js

@@ -142,24 +142,6 @@ exports.cachedResult = function cachedResult(fn) {
   };
 };
 
-/*
- * Implementation of ToInteger as per ECMAScript Specification
- * Refer: http://www.ecma-international.org/ecma-262/6.0/#sec-tointeger
- */
-const toInteger = exports.toInteger = function toInteger(argument) {
-  const number = +argument;
-  return Number.isNaN(number) ? 0 : Math.trunc(number);
-};
-
-/*
- * Implementation of ToLength as per ECMAScript Specification
- * Refer: http://www.ecma-international.org/ecma-262/6.0/#sec-tolength
- */
-exports.toLength = function toLength(argument) {
-  const len = toInteger(argument);
-  return len <= 0 ? 0 : Math.min(len, Number.MAX_SAFE_INTEGER);
-};
-
 // Useful for Wrapping an ES6 Class with a constructor Function that
 // does not require the new keyword. For instance:
 //   class A { constructor(x) {this.x = x;}}