Fix mouse lock perf issue on Windows.

content/browser/renderer_host/render_widget_host_view_win.h

Index: content/browser/renderer_host/render_widget_host_view_win.h
diff --git a/content/browser/renderer_host/render_widget_host_view_win.h b/content/browser/renderer_host/render_widget_host_view_win.h
index 0424f7a18b9b08fc4fd193b60d5619c35496c73f..d1426f600cde2355d644c24d068c66fe3cd2c8fe 100644
--- a/content/browser/renderer_host/render_widget_host_view_win.h
+++ b/content/browser/renderer_host/render_widget_host_view_win.h
@@ -335,7 +335,9 @@ class RenderWidgetHostViewWin
                                DWORD ex_style);
 
   CPoint GetClientCenter() const;
-  void MoveCursorToCenter() const;
+  // In mouse lock mode, moves the mouse cursor to the center of the view if it
+  // is too close to the border.
+  void MoveCursorToCenterIfNecessary();
 
   void HandleLockedMouseEvent(UINT message, WPARAM wparam, LPARAM lparam);
 
@@ -479,12 +481,20 @@ class RenderWidgetHostViewWin
   bool is_fullscreen_;
 
   // Used to record the last position of the mouse.
-  // While the mouse is locked, they store the last known position just as mouse
-  // lock was entered.
+  // While the mouse is locked, |last_unlocked_mouse_position_| and
+  // |last_unlocked_global_mouse_position_| store the last known position just
+  // as mouse lock was entered.
   // Relative to the upper-left corner of the view.
-  gfx::Point last_mouse_position_;
+  gfx::Point last_unlocked_mouse_position_;
   // Relative to the upper-left corner of the screen.
-  gfx::Point last_global_mouse_position_;
+  gfx::Point last_unlocked_global_mouse_position_;
+  // Valid while the mouse is locked.
+  gfx::Point last_locked_global_mouse_position_;
+
+  // When the mouse cursor is moved to the center of the view by
+  // MoveCursorToCenterIfNecessary(), we ignore the resulting WM_MOUSEMOVE
+  // message.
+  bool ignore_move_to_center_message_;
 
   // In the case of the mouse being moved away from the view and then moved
   // back, we regard the mouse movement as (0, 0).