Fixed overlapping subtle notifications on Mac.

chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.mm

Index: chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.mm
diff --git a/chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.mm b/chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.mm
index 0b4da465a4e6a1f3497aeab9d280322436ab0477..d2a2bda041dd27d53fc3a7685886bed95f9ff156 100644
--- a/chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.mm
+++ b/chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.mm
@@ -34,10 +34,16 @@ ExclusiveAccessController::ExclusiveAccessController(
 ExclusiveAccessController::~ExclusiveAccessController() {}
 
 void ExclusiveAccessController::Show() {
+  // Hide the backspace shortcut bubble, to avoid overlapping.
+  new_back_shortcut_bubble_.reset();
+
   views_bubble_.reset(new ExclusiveAccessBubbleViews(this, url_, bubble_type_));
 }
 
 void ExclusiveAccessController::ShowNewBackShortcutBubble(bool forward) {
+  // Hide the exclusive access bubble, to avoid overlapping.
+  views_bubble_.reset();
+
   if (new_back_shortcut_bubble_)
     new_back_shortcut_bubble_->UpdateContent(forward);
   else