Sorting breaks resizing

[sofoklisM]

Sorting in data grid breaks resizing.

For one thing the the offset and width of the header are incorrect once the header is sorted.
But what's worse is that DataGrid does not propagate the events to the Header because
headerBuilder.isHeader returns false for a column that's sorted.
That seems to me like DataGrid bug.

That's from AbstractCellTable.onBrowserEvent2

    /*
     * Look for the most immediate header parent if not already found. Its
     * possible that the footer or header will mistakenly identify a header
     * from the other section, so we remember both. When we eventually reach
     * the target table section element, we'll know for sure if its a header
     * of footer.
     */
    if (headerParent == null && headerBuilder.isHeader(cur)) {
      headerParent = cur;
    }

   ....
  boolean shouldSortColumn = true;
  // Fire the event to the header.
  if (headerParent != null) {
    Header<?> header =
        isHeader ? headerBuilder.getHeader(headerParent) : footerBuilder
            .getHeader(footerParent);

    if (header != null) {
      int headerIndex = isHeader ? headerBuilder.getRowIndex(targetTableRow) :
          footerBuilder.getRowIndex(targetTableRow);
      Context context = new Context(headerIndex, col, header.getKey());

      if (cellConsumesEventType(header.getCell(), eventType)) {          
        header.onBrowserEvent(context, headerParent, event);
      }

      if (isSelect) {
        // Preview the event, and possibily disable the column sort event. The event preview is
        // forced even if the header cell does not consume click event
        shouldSortColumn = header.onPreviewColumnSortEvent(context, headerParent, event);
      }
    }
  }