chore(keycodes): add comma to keycodes and update usages (#7852)

Author: amcdnl

src/cdk/keycodes/keycodes.ts

@@ -24,3 +24,4 @@ export const A = 65;
 export const Z = 90;
 export const ZERO = 48;
 export const NINE = 91;
+export const COMMA = 188;

src/demo-app/chips/chips-demo.ts

@@ -1,9 +1,7 @@
-import {ENTER} from '@angular/cdk/keycodes';
+import {ENTER, COMMA} from '@angular/cdk/keycodes';
 import {Component} from '@angular/core';
 import {MatChipInputEvent} from '@angular/material';
 
-const COMMA = 188;
-
 export interface Person {
   name: string;
 }

src/lib/chips/chip-input.spec.ts

@@ -1,5 +1,5 @@
 import {Directionality} from '@angular/cdk/bidi';
-import {ENTER} from '@angular/cdk/keycodes';
+import {ENTER, COMMA} from '@angular/cdk/keycodes';
 import {PlatformModule} from '@angular/cdk/platform';
 import {createKeyboardEvent} from '@angular/cdk/testing';
 import {Component, DebugElement} from '@angular/core';
@@ -9,8 +9,6 @@ import {MatChipInput, MatChipInputEvent} from './chip-input';
 import {MatChipsModule} from './index';
 
 
-const COMMA = 188;
-
 describe('MatChipInput', () => {
   let fixture: ComponentFixture<any>;
   let testChipInput: TestChipInput;

src/material-examples/chips-input/chips-input-example.ts

@@ -1,8 +1,6 @@
 import {Component} from '@angular/core';
 import {MatChipInputEvent} from '@angular/material';
-import {ENTER} from '@angular/cdk/keycodes';
-
-const COMMA = 188;
+import {ENTER, COMMA} from '@angular/cdk/keycodes';
 
 /**
  * @title Chips with input