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

chrome/browser/ui/cocoa/download/download_shelf_controller.mm

Index: chrome/browser/ui/cocoa/download/download_shelf_controller.mm
diff --git a/chrome/browser/ui/cocoa/download/download_shelf_controller.mm b/chrome/browser/ui/cocoa/download/download_shelf_controller.mm
index ebebb03f18c96560117ed7c28b07ca535c560912..fafbb78d8d59b9a92fa75c743133c378e3d56390 100644
--- a/chrome/browser/ui/cocoa/download/download_shelf_controller.mm
+++ b/chrome/browser/ui/cocoa/download/download_shelf_controller.mm
@@ -142,13 +142,26 @@ const NSSize kHoverCloseButtonDefaultSize = { 18, 18 };
 }
 
 - (void)dealloc {
+  [self browserWillBeDestroyed];
+  [super dealloc];
+}
+
+- (void)browserWillBeDestroyed {
   [[NSNotificationCenter defaultCenter] removeObserver:self];
-  [self cancelAutoClose];
+
+  // We need to explicitly release our download controllers here since they need
+  // to remove themselves as observers before the remaining shutdown happens.
+  [[self animatableView] stopAnimation];
   [self removeTrackingArea];
+  [self cancelAutoClose];
+  while ([downloadItemControllers_ count] > 0) {
+    [self removeDownload:[downloadItemControllers_ lastObject]
+          isShelfClosing:YES];
+  }
+  downloadItemControllers_.reset();
 
-  // The controllers will unregister themselves as observers when they are
-  // deallocated. No need to do that here.
-  [super dealloc];
+  bridge_.reset();
+  navigator_ = nullptr;
 }
 
 // Called after the frame's rect has changed; usually when the height is
@@ -213,19 +226,6 @@ const NSSize kHoverCloseButtonDefaultSize = { 18, 18 };
   [self maybeAutoCloseAfterDelay];
 }
 
-// We need to explicitly release our download controllers here since they need
-// to remove themselves as observers before the remaining shutdown happens.
-- (void)exiting {
-  [[self animatableView] stopAnimation];
-  [self removeTrackingArea];
-  [self cancelAutoClose];
-  while ([downloadItemControllers_ count] > 0) {
-    [self removeDownload:[downloadItemControllers_ lastObject]
-          isShelfClosing:YES];
-  }
-  downloadItemControllers_.reset();
-}
-
 - (void)showDownloadShelf:(BOOL)show
              isUserAction:(BOOL)isUserAction {
   [self cancelAutoClose];