Fix grammatical errors in comments in ui/views

ui/views/widget/tooltip_manager_win.cc

 // Copyright (c) 2011 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/views/widget/tooltip_manager_win.h"
 
 #include <windowsx.h>
 
 #include <limits>
 
@@ skipping 225 matching lines @@
   if (!monitor_bounds.Contains(gfx::Rect(bounds))) {
     return false;
   }
 
   ::SetWindowPos(tooltip_hwnd_, NULL, bounds.left, bounds.top, 0, 0,
                  SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOSIZE);
   return true;
 }
 
 int TooltipManagerWin::CalcTooltipHeight() {
-  // Ask the tooltip for it's font.
+  // Ask the tooltip for its font.
   int height;
   HFONT hfont = reinterpret_cast<HFONT>(
       SendMessage(tooltip_hwnd_, WM_GETFONT, 0, 0));
   if (hfont != NULL) {
     HDC dc = GetDC(tooltip_hwnd_);
     HFONT previous_font = static_cast<HFONT>(SelectObject(dc, hfont));
     int last_map_mode = SetMapMode(dc, MM_TEXT);
     TEXTMETRIC font_metrics;
     GetTextMetrics(dc, &font_metrics);
     height = font_metrics.tmHeight;
@@ skipping 125 matching lines @@
     keyboard_tooltip_hwnd_ = NULL;
   }
 }
 
 void TooltipManagerWin::DestroyKeyboardTooltipWindow(HWND window_to_destroy) {
   if (keyboard_tooltip_hwnd_ == window_to_destroy)
     HideKeyboardTooltip();
 }
 
 }  // namespace views