[rAC, OSX] Use bubble windows for error messages.

chrome/browser/ui/cocoa/base_bubble_controller.mm

Index: chrome/browser/ui/cocoa/base_bubble_controller.mm
diff --git a/chrome/browser/ui/cocoa/base_bubble_controller.mm b/chrome/browser/ui/cocoa/base_bubble_controller.mm
index fad938f381753510dd6ebe7abd54b47d80ef7c56..f08179b252be6a90089e14cb7b474b9b067e1982 100644
--- a/chrome/browser/ui/cocoa/base_bubble_controller.mm
+++ b/chrome/browser/ui/cocoa/base_bubble_controller.mm
@@ -210,6 +210,11 @@
       addLocalMonitorForEventsMatchingMask:NSLeftMouseDownMask
       handler:^NSEvent* (NSEvent* event) {
           if (event.window != window) {
+            // Ignore this event if the window isn't key - in that case, it
+            // can't resign key status in the first place.
+            if (![window isKeyWindow])
+              return event;
+
             // Call via the runloop because this block is called in the
             // middle of event dispatch.
             [self performSelector:@selector(windowDidResignKey:)