Dark theme: fix regressions

- Reply button stopped being styled because its class name changed.
- CL:1568 removed styles for |material-checkbox .content|
  unintentionally.
- Also, minor change: removed styles for checkboxes in the settings page
  which are no longer applied.

Change-Id: I76487cc5bb0e13411cfbac59afe100c089cb4ccb
diff --git a/src/static/css/ccdarktheme.css b/src/static/css/ccdarktheme.css
index 8bbef29..735e211 100644
--- a/src/static/css/ccdarktheme.css
+++ b/src/static/css/ccdarktheme.css
@@ -822,7 +822,8 @@
 }
 
 /* Checkbox input */
-material-checkbox material-icon {
+material-checkbox material-icon,
+    material-checkbox .content {
   color: var(--TWPT-secondary-text)!important;
 }
 
@@ -975,7 +976,8 @@
 }
 
 /* Reply button */
-material-fab.reply-button {
+material-fab.reply-button,
+    material-fab.reply-fab {
   background-color: var(--TWPT-link)!important;
   color: var(--TWPT-primary-background)!important;
 }
@@ -989,10 +991,6 @@
   color: var(--TWPT-secondary-text)!important;
 }
 
-ec-settings material-checkbox, ec-settings material-checkbox .content {
-  color: var(--TWPT-primary-text)!important;
-}
-
 /* Loading spinner */
 material-spinner {
   border-color: var(--TWPT-blue-A100)!important;