revert some changes

Author: tinayuangao

src/lib/checkbox/checkbox.html

@@ -35,7 +35,6 @@
       <div class="mat-checkbox-mixedmark"></div>
     </div>
   </div>
-
   <span class="mat-checkbox-label" #labelWrapper>
     <!-- Add an invisible span so JAWS can read the label -->
     <span style="display:none">&nbsp;</span>

src/lib/checkbox/checkbox.scss

@@ -418,6 +418,13 @@ $_mat-checkbox-mark-stroke-size: 2 / 15 * $mat-checkbox-size !default;
   }
 }
 
+mat-checkbox-input {
+  // Move the input to the bottom and in the middle.
+  // Visual improvement to properly show browser popups when being required.
+  bottom: 0;
+  left: 50%;
+}
+
 .mat-checkbox-ripple {
   position: absolute;
   left: -$_mat-checkbox-ripple-size;

src/lib/radio/radio.html

@@ -10,6 +10,7 @@
          [mdRippleDisabled]="_isRippleDisabled()"
          [mdRippleCentered]="true"></div>
   </div>
+
   <input #input class="mat-radio-input cdk-visually-hidden" type="radio"
          [id]="inputId"
          [checked]="checked"