Tagpicker ie (#5962)

* Add IE example (for debugging only, not to be merged)

* Remove temporary example

* Prevent Autofill onInputChange from being called on inputs with a placeholder in IE

* Add change files

common/changes/@uifabric/utilities/tagpicker-ie_2018-08-16-20-30.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "comment": "",
+      "packageName": "@uifabric/utilities",
+      "type": "none"
+    }
+  ],
+  "packageName": "@uifabric/utilities",
+  "email": "kakje@microsoft.com"
+}

common/changes/office-ui-fabric-react/tagpicker-ie_2018-08-16-20-30.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "office-ui-fabric-react",
+      "comment": "Autofill: prevent onInputChange from being called on IE11 inputs with a placeholder",
+      "type": "patch"
+    }
+  ],
+  "packageName": "office-ui-fabric-react",
+  "email": "kakje@microsoft.com"
+}

packages/office-ui-fabric-react/src/components/Autofill/Autofill.tsx

@@ -254,6 +254,11 @@ export class Autofill extends BaseComponent<IAutofillProps, IAutofillState> impl
    * @param newValue The new value from the input
    */
   private _updateValue = (newValue: string) => {
+    // Only proceed if the value is nonempty and is different from the old value
+    // This is to work around the fact that, in IE 11, inputs with a placeholder fire an onInput event on focus
+    if (!newValue && newValue === this._value) {
+      return;
+    }
     this._value = this.props.onInputChange ? this.props.onInputChange(newValue) : newValue;
     this.setState(
       {