Fix features in thread lists

Due to an update in the HTML structure of thread lists, many features
stopped working properly. This CL fixes these issues.

In the case of the "reduce whitespace" option, the thread list styles
applied in small screens have been temporarily removed since they have
to be fixed still.

Bug: twpowertools:138
Change-Id: Icf6d74f8a579fedb6af65f44864bd6f744098f2a
diff --git a/src/static/css/ccdarktheme.css b/src/static/css/ccdarktheme.css
index e912a8c..be6b4d9 100644
--- a/src/static/css/ccdarktheme.css
+++ b/src/static/css/ccdarktheme.css
@@ -55,6 +55,7 @@
 .material-content > header :is(material-button,
     material-button material-icon,
     .mdc-button.mdc-icon-button,
+    .mdc-button.mdc-icon-button material-icon,
     notification-bell material-icon) {
   color: rgba(255, 255, 255, .87)!important;
 }
@@ -311,7 +312,8 @@
  **/
 ec-thread-summary material-expansionpanel .action material-button,
     ec-thread-list material-checkbox material-icon,
-    ec-thread-summary material-expansionpanel .star-button:not(.starred) {
+    ec-thread-summary material-expansionpanel .star-button:not(.starred),
+    ec-thread-summary material-expansionpanel .mdc-button.mdc-icon-button material-icon {
   color: #696867!important; /* Custom value to match previous behavior */
   opacity: 1!important;
 }