Added the Ash.Tab.TimeBetweenSwitchToExistingTabUserActions histogram to track time between tab swit

chrome/browser/ui/views/tabs/tab.cc

Index: chrome/browser/ui/views/tabs/tab.cc
diff --git a/chrome/browser/ui/views/tabs/tab.cc b/chrome/browser/ui/views/tabs/tab.cc
index b03369a7918d754161ed9794680301fa4d346250..137c20917898a687fcbc2d9ffcadd6d62c10cb02 100644
--- a/chrome/browser/ui/views/tabs/tab.cc
+++ b/chrome/browser/ui/views/tabs/tab.cc
@@ -872,10 +872,12 @@ bool Tab::OnMousePressed(const ui::MouseEvent& event) {
       } else if (!IsSelected()) {
         controller_->SelectTab(this);
         content::RecordAction(UserMetricsAction("SwitchTab_Click"));
+        // TODO(bruthig):
       }
     } else if (!IsSelected()) {
       controller_->SelectTab(this);
       content::RecordAction(UserMetricsAction("SwitchTab_Click"));
+      // TODO(bruthig):
     }
     ui::MouseEvent cloned_event(event_in_parent, parent(),
                                 static_cast<View*>(this));