Fix fastdom-strict callbacks not being called with context (fixes #108)…

… (#109)

src/fastdom-strict.js

@@ -18,16 +18,18 @@ var debug = 0 ? console.log.bind(console, '[fastdom-strict]') : function() {};
 var enabled = false;
 
 window.fastdom = module.exports = fastdom.extend({
-  measure: function(task, ctx) {
+  measure: function(fn, ctx) {
     debug('measure');
+    var task = !ctx ? fn : fn.bind(ctx);
     return this.fastdom.measure(function() {
       if (!enabled) return task();
       return strictdom.phase('measure', task);
     }, ctx);
   },
 
-  mutate: function(task, ctx) {
+  mutate: function(fn, ctx) {
     debug('mutate');
+    var task = !ctx ? fn : fn.bind(ctx);
     return this.fastdom.mutate(function() {
       if (!enabled) return task();
       return strictdom.phase('mutate', task);

test/fastdom-strict-test.js

@@ -2,6 +2,7 @@
 /*jshint maxlen:false*/
 
 suite('fastdom-strict', function() {
+  var raf = window.requestAnimationFrame;
   var fastdom;
   var el;
 
@@ -75,4 +76,21 @@ suite('fastdom-strict', function() {
       el.clientWidth;
     }).then(done);
   });
+
+  test('callback is called with correct context when measuring and mutating', function(done) {
+    var ctx1 = { foo: 'bar' };
+    var ctx2 = { bar: 'baz' };
+
+    var spy1 = sinon.spy();
+    var spy2 = sinon.spy();
+
+    fastdom.measure(spy1, ctx1);
+    fastdom.mutate(spy2, ctx2);
+
+    raf(function() {
+      assert(spy1.calledOn(ctx1));
+      assert(spy2.calledOn(ctx2));
+      done();
+    });
+  });
 });