message: fix(devtools): set proper directive item and explorer height
  Fix rangle/angular-devtools#551
diff: @@ -63,7 +63,7 @@ export class DirectiveForestComponent implements OnInit, OnDestroy {
  (node) => node.expandable
  );
  readonly dataSource = new ComponentDataSource(this.treeControl);
  - readonly itemHeight = 21;
  + readonly itemHeight = 24;
  private _initialized = false;
  @@ -129,7 +129,8 @@ export class DirectiveForestComponent implements OnInit, OnDestroy {
  // The top most point we see an element
  const top = scrollParent.scrollTop;
  // That's the bottom most point we currently see an element.
  - const bottom = top + scrollParent.offsetHeight;
  + const parentHeight = scrollParent.offsetHeight;
  + const bottom = top + parentHeight;
  const idx = this.dataSource.expandedDataValues.findIndex((el) => el.id === node.id);
  // The node might be hidden.
  if (idx < 0) {
  @@ -139,7 +140,7 @@ export class DirectiveForestComponent implements OnInit, OnDestroy {
  if (itemTop < top) {
  scrollParent.scrollTo({ top: itemTop });
  } else if (bottom < itemTop + this.itemHeight) {
  - scrollParent.scrollTo({ top: itemTop - scrollParent.offsetHeight + this.itemHeight });
  + scrollParent.scrollTo({ top: itemTop - parentHeight + this.itemHeight });
  }
  }
  