Add support for movementX/Y in SyntheticMouseEvent

Register screenX/Y after calculating values

Fix movementY variable name error

Linting fix

src/renderers/dom/client/syntheticEvents/SyntheticMouseEvent.js

@@ -13,6 +13,7 @@
 
 var SyntheticUIEvent = require('SyntheticUIEvent');
 var ViewportMetrics = require('ViewportMetrics');
+var MouseMetrics = require('MouseMetrics');
 
 var getEventModifierState = require('getEventModifierState');
 
@@ -63,6 +64,20 @@ var MouseEventInterface = {
       event.pageY :
       event.clientY + ViewportMetrics.currentScrollTop;
   },
+  movementX: function(event) {
+    const movementX = 'movementX' in event ?
+      event.movementX :
+      event.screenX - MouseMetrics.previousScreenX;
+    MouseMetrics.setPreviousScreenX(event.screenX);
+    return movementX;
+  },
+  movementY: function(event) {
+    const movementY = 'movementY' in event ?
+      event.movementY :
+      event.screenY - MouseMetrics.previousScreenY;
+    MouseMetrics.setPreviousScreenY(event.screenY);
+    return movementY;
+  },
 };
 
 /**

src/renderers/dom/client/utils/MouseMetrics.js

@@ -0,0 +1,30 @@
+/**
+ * Copyright 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule MouseMetrics
+ */
+
+'use strict';
+
+var MouseMetrics = {
+
+  previousScreenX: 0,
+
+  previousScreenY: 0,
+
+  setPreviousScreenX: function(value) {
+    MouseMetrics.previousScreenX = value;
+  },
+
+  setPreviousScreenY: function(value) {
+    MouseMetrics.previousScreenY = value;
+  },
+
+};
+
+module.exports = MouseMetrics;