Canvas2d: Fix incorrect alignment of hit region when applied css/zoom.

third_party/WebKit/LayoutTests/fast/canvas/resources/test-helpers.js

+function coroutine(generator) {
+  var g = generator();
+  var promise = g.next().value;
+  function result(r) {
+    promise = g.next(r).value;
+    promise && promise.then(result);
+  }
+  promise.then(result)
+}
+
+function clickOrTouch(x, y) {
+  return new Promise(function(resolve, reject) {
+    window.ontouchstart = function(e) {
+      if (!window.eventSender)
+        console.log('x: ' + e.pageX, ', y: ' + e.pageY, ', region: ' + e.region);
+      resolve(e.targetTouches[0].region);
+    };
+
+    window.onclick = function(e) {
+      if (!window.eventSender)
+        console.log('x: ' + e.pageX, ', y: ' + e.pageY, ', region: ' + e.region);
+      resolve(e.region);
+    };
+
+    if (window.eventSender) {
+      eventSender.clearTouchPoints();
+      eventSender.addTouchPoint(x, y);
+      eventSender.touchStart();
+      eventSender.touchEnd();
+
+      eventSender.mouseMoveTo(x, y);
+      eventSender.mouseDown();
+      eventSender.mouseUp();
+    }
+  });
+}
+
+function createFace(context) {
+  context.fillStyle = 'pink';
+  context.arc(200, 175, 150, 0, Math.PI * 2, true);
+  context.fill();
+  context.addHitRegion({ id : 'face', control : document.getElementById('face') });
+
+  context.beginPath();
+  context.fillStyle = 'black';
+  context.globalAlpha = .5;
+  context.moveTo(200, 165);
+  context.lineTo(240, 205);
+  context.lineTo(160, 205);
+  context.closePath();
+  context.fill();
+  context.addHitRegion({ id : 'nose' });
+
+  context.beginPath();
+  context.fillStyle = 'red';
+  context.rect(125, 240, 150, 20);
+  context.fill();
+  context.addHitRegion({ id : 'mouth' });
+
+  context.beginPath();
+  context.globalAlpha = 1;
+  context.fillStyle = 'blue';
+  context.arc(150, 125, 25, 0, Math.PI * 2, true);
+  context.arc(250, 125, 25, 0, Math.PI * 2, true);
+  context.fill();
+  context.addHitRegion({ id: 'eye', control : document.getElementById('eyes') });
+}