Even earlier exit for linear case.

I have an application which evaluates lots of different beziers, where there's a high chance they might be linear. This is a simple optimisation for that case. Also in my opinion, this layout is slightly easier to follow.

src/index.js

@@ -51,17 +51,23 @@ function newtonRaphsonIterate (aX, aGuessT, mX1, mX2) {
  return aGuessT;
 }
 
+function LinearEasing (x) {
+  return x;
+}
+
 module.exports = function bezier (mX1, mY1, mX2, mY2) {
   if (!(0 <= mX1 && mX1 <= 1 && 0 <= mX2 && mX2 <= 1)) {
     throw new Error('bezier x values must be in [0, 1] range');
   }
 
+  if (mX1 === mY1 && mX2 === mY2) {
+    return LinearEasing;
+  }
+
   // Precompute samples table
   var sampleValues = float32ArraySupported ? new Float32Array(kSplineTableSize) : new Array(kSplineTableSize);
-  if (mX1 !== mY1 || mX2 !== mY2) {
-    for (var i = 0; i < kSplineTableSize; ++i) {
-      sampleValues[i] = calcBezier(i * kSampleStepSize, mX1, mX2);
-    }
+  for (var i = 0; i < kSplineTableSize; ++i) {
+    sampleValues[i] = calcBezier(i * kSampleStepSize, mX1, mX2);
   }
 
   function getTForX (aX) {
@@ -89,9 +95,6 @@ module.exports = function bezier (mX1, mY1, mX2, mY2) {
   }
 
   return function BezierEasing (x) {
-    if (mX1 === mY1 && mX2 === mY2) {
-      return x; // linear
-    }
     // Because JavaScript number are imprecise, we should guarantee the extremes are right.
     if (x === 0) {
       return 0;