Bug 89971 [Viewers] Viewers that use IViewerLabelProvider do too many instanceof checks
M6 Checking our viewer the calls to buildLabel are doing too many instanceof checks. As a result certain viewers (such as the table viewer) are twice as slow as they were in 3.0 due to these checks. I have written some performance suites to test the Table, Tree, List and Combo viewers. Table and Tree have this issue.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/StructuredViewer.java
* supported types.
	 * @param provider
	 */
	protected void assertContentProviderType(IContentProvider provider) {
		Assert.isTrue(provider instanceof IStructuredContentProvider);
	}
	/*
	 *  (non-Javadoc)
	 * @see org.eclipse.jface.viewers.Viewer#setInput(java.lang.Object)
	 */
	public final void setInput(Object input) {
		try {
			
			unmapAllElements();
			super.setInput(input);
		} finally {
			
		}
	}
	/*
	 *  (non-Javadoc)
	 * @see org.eclipse.jface.viewers.Viewer#setSelection(org.eclipse.jface.viewers.ISelection, boolean)
	 */
	public void setSelection(ISelection selection, boolean reveal) {
		/**
		 * <p>
		 * If the new selection differs from the current selection the hook
		 * <code>updateSelection</code> is called.
		 * </p>
		 * <p>