Don't retain the WebView, otherwise we get a retain cycle, because th…

…e WebView owns us. This can lead to a crash on quit in +[WebView closeAllWebViews]

Plugin/Plugin.m

@@ -1601,8 +1601,7 @@ - (WebView *)webView
 }
 - (void)setWebView:(WebView *)newValue
 {
-    [newValue retain];
-    [_webView release];
+    // Not retained, because the WebView owns the plugin, so we'll get a retain cycle.
     _webView = newValue;
 }