Bug 1164784 - Eliminate CSS duplication with perf tool record button. r=jsantell

browser/devtools/performance/performance.xul

@@ -146,7 +146,8 @@
           <hbox class="devtools-toolbarbutton-group"
                 pack="center">
             <toolbarbutton class="devtools-toolbarbutton record-button"
-                           label="&profilerUI.startRecording;" />
+                           label="&profilerUI.startRecording;"
+                           standalone="true"/>
           </hbox>
         </hbox>
         <vbox id="performance-view-content" flex="1">
@@ -172,7 +173,8 @@
                 <hbox class="devtools-toolbarbutton-group"
                       pack="center">
                   <toolbarbutton class="devtools-toolbarbutton record-button"
-                                 label="&profilerUI.stopRecording;" />
+                                 label="&profilerUI.stopRecording;"
+                                 standalone="true"/>
                 </hbox>
                 <label class="realtime-disabled-message">
                   Realtime recording data disabled on non-multiprocess Firefox.

browser/themes/shared/devtools/performance.inc.css

@@ -84,28 +84,15 @@
   margin: 3px 2px;
 }
 
-.theme-dark #performance-view toolbarbutton.record-button {
-  background-color: var(--theme-tab-toolbar-background);
-  border: 1px solid var(--theme-sidebar-background);
-}
-
-.theme-light #performance-view toolbarbutton.record-button {
-  background-color: rgba(221, 221, 221, 1);
-  border: 1px solid rgba(204, 204, 204, 1);
-}
-
-#performance-view toolbarbutton.record-button {
-  margin: 5px;
-  padding: 5px;
-  cursor: pointer;
-  text-shadow: none;
-}
-
 #performance-view .realtime-message {
   opacity: 0.5;
   display: block;
 }
 
+#performance-view toolbarbutton.record-button {
+  padding: 5px;
+}
+
 #performance-view toolbarbutton.record-button[checked],
 #performance-view toolbarbutton.record-button[checked] {
   color: var(--theme-selection-color);