fix(select): md-checkbox inside md-list-item using incorrect text color.

Closes #7893

Author: Derek Louie

src/components/select/select-theme.scss

@@ -71,10 +71,10 @@ md-select-menu.md-THEME_NAME-theme {
 }
 
 
-[md-checkbox-enabled].md-THEME_NAME-theme {
+.md-checkbox-enabled.md-THEME_NAME-theme {
   @include checkbox-primary('[selected]');
 
-  md-option ._md-text {
+  md-option .md-text {
     color: '{{background-900-0.87}}';
   }
 }

src/components/select/select.js

@@ -790,7 +790,7 @@ function OptionDirective($mdButtonInkRipple, $mdUtil) {
     var selectCtrl = ctrls[1];
 
     if (selectCtrl.isMultiple) {
-      element.attr('md-checkbox-enabled', '');
+      element.addClass('_md-checkbox-enabled');
       element.prepend(CHECKBOX_SELECTION_INDICATOR.clone());
     }
 

src/components/select/select.scss

@@ -233,7 +233,7 @@ md-optgroup {
 }
 
 md-select-menu[multiple] {
-  md-option[md-checkbox-enabled] {
+  md-option._md-checkbox-enabled {
     @include rtl(padding-left, $select-option-padding * 2.5, $select-option-padding);
     @include rtl(padding-right, $select-option-padding, $select-option-padding * 2.5);