Fix checkbox label not read in JAWS

Author: tinayuangao

src/lib/checkbox/checkbox.html

@@ -1,4 +1,4 @@
-<label class="mat-checkbox-layout" #label>
+<div class="mat-checkbox-layout">
   <div class="mat-checkbox-inner-container"
        [class.mat-checkbox-inner-container-no-side-margin]="!_hasLabel()">
     <input #input
@@ -35,7 +35,9 @@
       <div class="mat-checkbox-mixedmark"></div>
     </div>
   </div>
-  <span class="mat-checkbox-label" #labelWrapper>
-    <ng-content></ng-content>
-  </span>
-</label>
+  <label [attr.for]="inputId" #label>
+    <span class="mat-checkbox-label" #labelWrapper>
+      <ng-content></ng-content>
+    </span>
+  </label>
+</div>