feat(ngModel):handle ime events (#13891)

PR Close: #13891

modules/@angular/forms/src/directives/ng_model.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Directive, Host, Inject, Input, OnChanges, OnDestroy, Optional, Output, Self, SimpleChanges, forwardRef} from '@angular/core';
+import {Directive, Host, HostListener, Inject, Input, OnChanges, OnDestroy, Optional, Output, Self, SimpleChanges, forwardRef} from '@angular/core';
 
 import {EventEmitter} from '../facade/async';
 import {FormControl} from '../model';
@@ -115,6 +115,7 @@ export class NgModel extends NgControl implements OnChanges,
   _control = new FormControl();
   /** @internal */
   _registered = false;
+  private _composing = false;
   viewModel: any;
 
   @Input() name: string;
@@ -124,6 +125,15 @@ export class NgModel extends NgControl implements OnChanges,
 
   @Output('ngModelChange') update = new EventEmitter();
 
+  @HostListener('compositionstart')
+  compositionStart(): void { this._composing = true; }
+
+  @HostListener('compositionend')
+  compositionEnd(): void {
+    this._composing = false;
+    this.update.emit(this.viewModel);
+  }
+
   constructor(@Optional() @Host() parent: ControlContainer,
               @Optional() @Self() @Inject(NG_VALIDATORS) validators: Array<Validator|ValidatorFn>,
               @Optional() @Self() @Inject(NG_ASYNC_VALIDATORS) asyncValidators: Array<Validator|AsyncValidatorFn>,
@@ -167,7 +177,7 @@ export class NgModel extends NgControl implements OnChanges,
 
               viewToModelUpdate(newValue: any): void {
                 this.viewModel = newValue;
-                this.update.emit(newValue);
+                !this._composing && this.update.emit(newValue);
               }
 
               private _setUpControl(): void {