Update ctrl+click/drag documentation

tracing/tracing/ui/timeline_view_help_overlay.html

Index: tracing/tracing/ui/timeline_view_help_overlay.html
diff --git a/tracing/tracing/ui/timeline_view_help_overlay.html b/tracing/tracing/ui/timeline_view_help_overlay.html
index ec06f720c5ab15cc9dc20e21d5e5551b472ff384..bb06c80dbace7f3706ed674774c324c552c9b175 100644
--- a/tracing/tracing/ui/timeline_view_help_overlay.html
+++ b/tracing/tracing/ui/timeline_view_help_overlay.html
@@ -111,6 +111,11 @@ found in the LICENSE file.
       </div>
 
       <div class='pair'>
+        <div class='command'><span class='mod'></span>-click/drag</div>
+        <div class='action'>Add events to the current selection</div>
+      </div>
+
+      <div class='pair'>
         <div class='command'>double click</div>
         <div class='action'>Select all events with same title</div>
       </div>
@@ -166,11 +171,6 @@ found in the LICENSE file.
       </div>
 
       <div class='pair'>
-        <div class='command'><span class='mod'></span></div>
-        <div class='action'>Hold for temporary zoom</div>
-      </div>
-
-      <div class='pair'>
         <div class='command'>/</div>
         <div class='action'>Search</div>
       </div>