Ensure that mouse lock works correctly on Chrome ASH in Windows 8.

ui/aura/remote_window_tree_host_win.cc

Index: ui/aura/remote_window_tree_host_win.cc
diff --git a/ui/aura/remote_window_tree_host_win.cc b/ui/aura/remote_window_tree_host_win.cc
index 14c9bf6fe6cfa77813edeb5ba1900e1fbdf25077..f939ccbf75dbc2eaeafb895126b08b18b864fdd1 100644
--- a/ui/aura/remote_window_tree_host_win.cc
+++ b/ui/aura/remote_window_tree_host_win.cc
@@ -93,7 +93,7 @@ RemoteWindowTreeHostWin* RemoteWindowTreeHostWin::Instance() {
 RemoteWindowTreeHostWin::RemoteWindowTreeHostWin()
     : remote_window_(NULL),
       host_(NULL),
-      ignore_mouse_moves_until_set_cursor_ack_(false),
+      ignore_mouse_moves_until_set_cursor_ack_(0),
       event_flags_(0),
       window_size_(aura::WindowTreeHost::GetNativeScreenSize()) {
   CHECK(!g_instance);
@@ -262,7 +262,7 @@ void RemoteWindowTreeHostWin::MoveCursorToNative(const gfx::Point& location) {
   // this we invoke the SetCursor API in the viewer process and ignore
   // mouse messages until we received an ACK from the viewer indicating that
   // the SetCursor operation completed.
-  ignore_mouse_moves_until_set_cursor_ack_ = true;
+  ignore_mouse_moves_until_set_cursor_ack_++;
   VLOG(1) << "In MoveCursorTo. Sending IPC";
   host_->Send(new MetroViewerHostMsg_SetCursorPos(location.x(), location.y()));
 }
@@ -430,8 +430,8 @@ void RemoteWindowTreeHostWin::OnTouchMoved(int32 x,
 }
 
 void RemoteWindowTreeHostWin::OnSetCursorPosAck() {
-  DCHECK(ignore_mouse_moves_until_set_cursor_ack_);
-  ignore_mouse_moves_until_set_cursor_ack_ = false;
+  DCHECK_GT(ignore_mouse_moves_until_set_cursor_ack_, 0);
+  ignore_mouse_moves_until_set_cursor_ack_--;
 }
 
 ui::RemoteInputMethodPrivateWin*