Bug 286949 [Browser] Bad usage of URL#equals(Object) in WebBrowserEditorInput
HEAD WebBrowserEditorInput#equals(..) calls URL#equals(Object), but the latter resolves the host of the URLs via DNS lookups, which is most of the time not what you want. You should instead compare the strings from URL#toExternalForm(). Furthermore, WebBrowserEditorInput should also override hashCode() (equal objects must have equal hash codes). Note that URL#hashCode() is also broken, so you should use URL#toExternalForm() there as well.
bundles/org.eclipse.ui.browser/src/org/eclipse/ui/internal/browser/WebBrowserEditorInput.java
* input. @return the persistable element, or <code>null</code> if this
	 * editor input cannot be persisted
	 */
	public IPersistableElement getPersistable() {
		if ((style & IWorkbenchBrowserSupport.PERSISTENT) == 0)
			return null;
		return this;
	}
	public String getToolTipText() {
		if (tooltip != null)
			return tooltip;
		if (url != null)
			return url.toExternalForm();
		return Messages.viewWebBrowserTitle;
	}
	/**
	 * Returns the url.
	 * 
	 * @return java.net.URL
	 */
	public URL getURL() {
		return url;
	}
	/**
	 * Returns the browser id. Browsers with a set id will always & only be
	 * replaced by browsers with the same id.
	 * 
	 * @return String
	 */
	public String getBrowserId() {