Update chooser row view when mouse click down and move over rows

chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa_controller.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa_controller.h"
 
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/chooser_controller/chooser_controller.h"
 #import "chrome/browser/ui/cocoa/chooser_content_view_cocoa.h"
 #import "chrome/browser/ui/cocoa/extensions/chooser_dialog_cocoa.h"
@@ skipping 48 matching lines @@
 
 - (CGFloat)tableView:(NSTableView*)tableView heightOfRow:(NSInteger)row {
   return [chooserContentView_ tableRowViewHeight:row];
 }
 
 - (void)tableViewSelectionDidChange:(NSNotification*)aNotification {
   [chooserContentView_ updateContentRowColor];
   [connectButton_ setEnabled:[tableView_ numberOfSelectedRows] > 0];
 }
 
+// Selection changes (while the mouse button is still down).
+- (void)tableViewSelectionIsChanging:(NSNotification*)aNotification {
+  [chooserContentView_ updateContentRowColor];
+  [connectButton_ setEnabled:[tableView_ numberOfSelectedRows] > 0];
+}
+
 - (void)onConnect:(id)sender {
   [chooserContentView_ accept];
   chooserDialogCocoa_->Dismissed();
 }
 
 - (void)onCancel:(id)sender {
   [chooserContentView_ cancel];
   chooserDialogCocoa_->Dismissed();
 }
 
 - (ChooserContentViewCocoa*)chooserContentView {
   return chooserContentView_.get();
 }
 
 @end