Set explicit row heights in the Task Manager

With the macOS 11 SDK, the default row height in an NSTableView
changed. The modern view-based mode of NSTableView is not
consistent or fully functional across all the OS versions
supported by Chromium (see https://crbug.com/1147532#c1) so
fix by explicitly specifying the row height.

Fixed: 1147532
Change-Id: I6126e7126de5b8cfbb777b6ef5b997cf794c69ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532597
Commit-Queue: Avi Drissman <avi@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Auto-Submit: Avi Drissman <avi@chromium.org>
Reviewed-by: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826271}

chrome/browser/ui/cocoa/task_manager_mac.mm

@@ -535,6 +535,10 @@ NSString* ColumnIdentifier(int id) {
   return _tableModel->RowCount();
 }
 
+- (CGFloat)tableView:(NSTableView*)tableView heightOfRow:(NSInteger)row {
+  return 16;
+}
+
 - (NSString*)modelTextForRow:(int)row column:(int)columnId {
   DCHECK_LT(static_cast<size_t>(row), _viewToModelMap.size());
   return base::SysUTF16ToNSString(