Ensure calling Close and set_listener(NULL) on End().

WebContentsImpl's dtor calls End() but it may not cause
set_listener(NULL) in some case, which may cause a use-after-free.

This CL always reset them at End(). This would mean
DidEndColorChooser() may be called twice, so web_contents_
has to be reset to NULL once DidEndColorChooser() is called.

BUG=338464
R=keishi@chromium.org

Review URL: https://codereview.chromium.org/148223009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247917 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/views/color_chooser_aura.cc

@@ -35,7 +35,7 @@ void ColorChooserAura::OnColorChooserDialogClosed() {
 }
 
 void ColorChooserAura::End() {
-  if (widget_ && widget_->IsVisible()) {
+  if (widget_) {
     view_->set_listener(NULL);
     widget_->Close();
     view_ = NULL;