Aura tooltips do not move on mouse move in case of many neighboring views with the same label

ui/views/corewm/tooltip_controller.cc

Index: ui/views/corewm/tooltip_controller.cc
diff --git a/ui/views/corewm/tooltip_controller.cc b/ui/views/corewm/tooltip_controller.cc
index 86e9fd6c87ae2d59b8bc94da8d23628da26a732f..2bce79fa38c3c9088a261b3ef5b54abb3104f665 100644
--- a/ui/views/corewm/tooltip_controller.cc
+++ b/ui/views/corewm/tooltip_controller.cc
@@ -115,6 +115,7 @@ aura::Window* GetTooltipTarget(const ui::MouseEvent& event,
 
 TooltipController::TooltipController(scoped_ptr<Tooltip> tooltip)
     : tooltip_window_(NULL),
+      tooltip_id_(NULL),
       tooltip_window_at_mouse_press_(NULL),
       tooltip_(tooltip.Pass()),
       tooltips_enabled_(true) {
@@ -282,12 +283,23 @@ void TooltipController::UpdateIfRequired() {
     tooltip_window_at_mouse_press_ = NULL;
   }
 
+  // If the uniqueness indicator is different from the previously encountered
+  // one, we should force tooltip update
+  const void* tooltip_id = aura::client::GetTooltipId(tooltip_window_);
+  bool ids_differ = false;
+  if (tooltip_id) {

[sky, 2014/06/02 15:39:47]

Why the if here? Can't you always compare tooltip_id_ and tooltip_id?

+    ids_differ = tooltip_id_ != tooltip_id;
+    tooltip_id_ = tooltip_id;
+  } else {
+    tooltip_id_ = NULL;
+  }
+
   // We add the !tooltip_->IsVisible() below because when we come here from
   // TooltipTimerFired(), the tooltip_text may not have changed but we still
   // want to update the tooltip because the timer has fired.
   // If we come here from UpdateTooltip(), we have already checked for tooltip
   // visibility and this check below will have no effect.
-  if (tooltip_text_ != tooltip_text || !tooltip_->IsVisible()) {
+  if (tooltip_text_ != tooltip_text || !tooltip_->IsVisible() || ids_differ) {
     tooltip_shown_timer_.Stop();
     tooltip_text_ = tooltip_text;
     base::string16 trimmed_text(tooltip_text_);