Disable delegation to picker controller once it is deleted.

chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.mm

Index: chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.mm
diff --git a/chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.mm b/chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.mm
index 72edc4db91690e077103c01bcec06ced60aa77d5..63182990c35cbd80c9d572e368ef05287317e79c 100644
--- a/chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.mm
+++ b/chrome/browser/ui/cocoa/intents/web_intent_picker_cocoa2.mm
@@ -44,7 +44,7 @@ void WebIntentPickerCocoa2::Close() {
 }
 
 void WebIntentPickerCocoa2::SetActionString(const string16& action) {
-  // Ignored. Action string it retrieved from the model.
+  // Ignored. Action string is retrieved from the model.
 }
 
 void WebIntentPickerCocoa2::OnExtensionInstallSuccess(const std::string& id) {
@@ -84,6 +84,10 @@ void WebIntentPickerCocoa2::OnPendingAsyncCompleted() {
   [view_controller_ update];
 }
 
+void WebIntentPickerCocoa2::InvalidateDelegate() {
+  delegate_ = NULL;
+}
+
 void WebIntentPickerCocoa2::OnInlineDispositionWebContentsLoaded(
     content::WebContents* web_contents) {
   [view_controller_ update];
@@ -119,6 +123,7 @@ void WebIntentPickerCocoa2::OnConstrainedWindowClosed(
   model_->set_observer(NULL);
   model_ = NULL;
 
-  delegate_->OnClosing();
+  if (delegate_)
+    delegate_->OnClosing();
   MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }