Break path whereby AssociatedURLLoader::~AssociatedURLLoader() is re-entered on top of itself.

BUG=159429

Review URL: https://chromiumcodereview.appspot.com/11359222

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@168150 0039d316-1c4b-4281-b951-d872f2087c98
void PPB_URLLoader_Impl::Close() {
  if (loader_.get())
    loader_->cancel();
  else if (main_document_loader_)
    GetFrameForResource(this)->stopLoading();
}

void PPB_URLLoader_Impl::Close() {
  if (loader_.get())
    loader_->cancel();
  else if (main_document_loader_)
    GetFrameForResource(this)->stopLoading();
}
