[Mac] Inform reference counted objects that hold a weak Browser* when the Browser is being destroye…

chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_controller.mm

Index: chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_controller.mm
diff --git a/chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_controller.mm b/chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_controller.mm
index 14b691b3e49bdb67be302238d566ccad4124586b..795415f90a5d7515e406fcfa995c3b378ffe679a 100644
--- a/chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_controller.mm
+++ b/chrome/browser/ui/cocoa/find_bar/find_bar_cocoa_controller.mm
@@ -88,11 +88,16 @@ const float kRightEdgeOffset = 25;
 }
 
 - (void)dealloc {
+  [self browserWillBeDestroyed];
+  [super dealloc];
+}
+
+- (void)browserWillBeDestroyed {
   // All animations should have been explicitly stopped before a tab is closed.
   DCHECK(!showHideAnimation_.get());
   DCHECK(!moveAnimation_.get());
   [[NSNotificationCenter defaultCenter] removeObserver:self];
-  [super dealloc];
+  browser_ = nullptr;
 }
 
 - (void)setFindBarBridge:(FindBarBridge*)findBarBridge {