Fix some gramattical errors in comments in ui/aura

ui/aura/root_window.cc

 // Copyright (c) 2012 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.
 
 #include "ui/aura/root_window.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 841 matching lines @@
 void RootWindow::SynthesizeMouseMoveEvent() {
   if (!synthesize_mouse_move_)
     return;
   synthesize_mouse_move_ = false;
 #if !defined(OS_WIN)
   // Temporarily disabled for windows. See crbug.com/112222.
   gfx::Point orig_mouse_location = last_mouse_location_;
   layer()->transform().TransformPoint(orig_mouse_location);
 
   // TODO(derat|oshima): Don't use mouse_button_flags_ as it's
-  // is currently broken. See/ crbug.com/107931.
+  // currently broken. See/ crbug.com/107931.
   MouseEvent event(ui::ET_MOUSE_MOVED,
                    orig_mouse_location,
                    orig_mouse_location,
                    ui::EF_IS_SYNTHESIZED);
   DispatchMouseEvent(&event);
 #endif
 }
 
 }  // namespace aura