refactor(infrastructure): Use ES2015 import for MDC Foundation API's

* Use import instead of require

src/lib/checkbox/checkbox.component.ts

@@ -17,8 +17,8 @@ import { NG_VALUE_ACCESSOR, ControlValueAccessor } from '@angular/forms';
 import { MDCCheckboxAdapter } from './checkbox-adapter';
 import { Ripple } from '.././ripple/ripple.directive';
 
-const { MDCFormField } = require('@material/form-field');
-const { MDCCheckboxFoundation } = require('@material/checkbox');
+import { MDCFormField } from '@material/form-field';
+import { MDCCheckboxFoundation } from '@material/checkbox';
 
 let formField_ = null;
 let nextElId_ = 0;

src/lib/form-field/form-field.component.ts

@@ -11,7 +11,7 @@ import {
 import { MDCFormFieldAdapter } from './form-field-adapter';
 import { CheckboxComponent } from '.././checkbox/checkbox.component';
 
-const { MDCFormField, MDCFormFieldFoundation } = require('@material/form-field');
+import { MDCFormField, MDCFormFieldFoundation } from '@material/form-field';
 
 @Component({
   selector: 'mdc-form-field',

src/lib/linear-progress/linear-progress.component.ts

@@ -9,7 +9,7 @@ import {
 } from '@angular/core';
 import { MDCLinearProgressAdapter } from './linear-progress-adapter';
 
-const { MDCLinearProgressFoundation } = require('@material/linear-progress');
+import { MDCLinearProgressFoundation } from '@material/linear-progress';
 
 @Component({
   selector: 'mdc-linear-progress',

src/lib/menu/menu-item.directive.ts

@@ -37,4 +37,4 @@ export class MenuItemDirective {
   constructor(
     private _renderer: Renderer2,
     private _root: ElementRef) { }
-}
+}

src/lib/menu/menu.component.ts

@@ -17,8 +17,8 @@ import { MDCMenuAdapter } from './menu-adapter';
 import { MenuItemDirective } from './menu-item.directive';
 import { isBrowser } from '../common/platform';
 
-const { MDCSimpleMenuFoundation } = require('@material/menu/simple');
-const { getTransformPropertyName } = require('@material/menu/util');
+import { MDCSimpleMenuFoundation } from '@material/menu/simple';
+import { getTransformPropertyName } from '@material/menu/util';
 
 export enum MDC_OPEN_FROM {
   TOP_LEFT = 'mdc-simple-menu--open-from-top-left',

src/lib/radio/radio.component.ts

@@ -17,8 +17,8 @@ import { NG_VALUE_ACCESSOR, RadioControlValueAccessor } from '@angular/forms';
 import { MDCRadioAdapter } from './radio-adapter';
 import { Ripple } from '.././ripple/ripple.directive';
 
-const { MDCFormField } = require('@material/form-field');
-const { MDCRadioFoundation } = require('@material/radio');
+import { MDCFormField } from '@material/form-field';
+import { MDCRadioFoundation } from '@material/radio';
 
 let formField_ = null;
 let nextElId_ = 0;

src/lib/ripple/ripple.directive.ts

@@ -5,9 +5,8 @@
   Renderer2
 } from '@angular/core';
 import { MDCRippleAdapter } from './ripple-adapter';
-import { supportsCssVariables } from '@material/ripple/util';
 
-const { MDCRippleFoundation } = require('@material/ripple');
+import { MDCRippleFoundation, util } from '@material/ripple';
 
 type UnlistenerMap = WeakMap<EventListener, Function>;
 
@@ -21,7 +20,7 @@ export class Ripple implements OnDestroy {
   private _unlisteners: Map<string, UnlistenerMap> = new Map<string, UnlistenerMap>();
 
   private _mdcAdapter: MDCRippleAdapter = {
-    browserSupportsCssVars: () => (typeof window !== 'undefined') ? supportsCssVariables(window) : false,
+    browserSupportsCssVars: () => (typeof window !== 'undefined') ? util.supportsCssVariables(window) : false,
     isUnbounded: () => this.unbounded,
     isSurfaceActive: () => this.active,
     isSurfaceDisabled: () => {

src/lib/snackbar/snackbar.component.ts

@@ -16,8 +16,8 @@ import { SnackbarActionWrapperDirective } from './snackbar-action-wrapper.direct
 import { SnackbarActionButtonDirective } from './snackbar-action-button.directive';
 import { isBrowser } from '../common/platform';
 
-const { MDCSnackbarFoundation } = require('@material/snackbar');
-const { getCorrectEventName } = require('@material/animation');
+import { MDCSnackbarFoundation } from '@material/snackbar';
+import { getCorrectEventName } from '@material/animation';
 
 type UnlistenerMap = WeakMap<EventListener, Function>;
 

src/lib/switch/switch.component.ts

@@ -15,7 +15,7 @@ import {
 import { NG_VALUE_ACCESSOR, ControlValueAccessor } from '@angular/forms';
 import { Ripple } from '.././ripple/ripple.directive';
 
-const { MDCFormField } = require('@material/form-field');
+import { MDCFormField } from '@material/form-field';
 
 export const MD_SWITCH_CONTROL_VALUE_ACCESSOR: Provider = {
   provide: NG_VALUE_ACCESSOR,

src/lib/textfield/textfield.component.ts

@@ -16,7 +16,7 @@
 import { NG_VALUE_ACCESSOR, ControlValueAccessor } from '@angular/forms';
 import { MDCTextfieldAdapter } from './textfield-adapter';
 
-const { MDCTextfieldFoundation } = require('@material/textfield');
+import { MDCTextfieldFoundation } from '@material/textfield';
 
 export const MD_TEXTFIELD_CONTROL_VALUE_ACCESSOR: Provider = {
   provide: NG_VALUE_ACCESSOR,

src/lib/toolbar/toolbar.component.ts

@@ -16,7 +16,7 @@ import { ToolbarTitleDirective } from './toolbar-title.directive';
 import { ToolbarRowDirective } from './toolbar-row.directive';
 import { isBrowser } from '../common/platform';
 
-const { MDCToolbarFoundation, util } = require('@material/toolbar');
+import { MDCToolbarFoundation, util } from '@material/toolbar';
 
 type UnlistenerMap = WeakMap<EventListener, Function>;