[Mac] Fix a crash in the cookies manager that was caused by an invalid selection.

chrome/browser/cocoa/cookies_window_controller.mm

Index: chrome/browser/cocoa/cookies_window_controller.mm
diff --git a/chrome/browser/cocoa/cookies_window_controller.mm b/chrome/browser/cocoa/cookies_window_controller.mm
index 8325f3a6102688412ec9d9aa5737e9cfd6b0e0f9..75e5060f356fc4fb8e6434697773ef4625e5aa28 100644
--- a/chrome/browser/cocoa/cookies_window_controller.mm
+++ b/chrome/browser/cocoa/cookies_window_controller.mm
@@ -128,6 +128,7 @@ CocoaCookieTreeNode* CookiesTreeModelObserverBridge::FindCocoaNode(
 
 @implementation CookiesWindowController
 
+@synthesize removeButtonEnabled = removeButtonEnabled_;
 @synthesize treeController = treeController_;
 
 - (id)initWithProfile:(Profile*)profile {
@@ -262,6 +263,33 @@ CocoaCookieTreeNode* CookiesTreeModelObserverBridge::FindCocoaNode(
   }
 }
 
+- (void)outlineViewSelectionDidChange:(NSNotification*)notif {
+  // Multi-selection should be disabled in the UI, but for sanity, double-check
+  // that they can't do it here.
+  NSUInteger count = [[treeController_ selectedObjects] count];
+  if (count != 1U) {
+    DCHECK_LT(count, 1U) << "User was able to select more than one cookie node!";
+    [self setRemoveButtonEnabled:NO];
+    return;
+  }
+
+  // Go through the selection's indexPath and make sure that the node that is
+  // being referenced actually exists in the Cocoa model.
+  NSIndexPath* selection = [treeController_ selectionIndexPath];
+  NSUInteger length = [selection length];
+  CocoaCookieTreeNode* node = [self cocoaTreeModel];
+  for (NSUInteger i = 0; i < length; ++i) {
+    NSUInteger childIndex = [selection indexAtPosition:i];
+    if (childIndex >= [[node children] count]) {
+      [self setRemoveButtonEnabled:NO];
+      return;
+    }
+    node = [[node children] objectAtIndex:childIndex];
+  }
+
+  [self setRemoveButtonEnabled:YES];
+}
+
 #pragma mark Unit Testing
 
 - (CookiesTreeModelObserverBridge*)modelObserver {