Reduce the fullscreen window height by 1px on activation loss.

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index f632827ca29663e93365929d151c4c1c5add9d49..f70dc276eadd0a3c25c49afceed05fe598c43830 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -333,6 +333,7 @@ HWNDMessageHandler::HWNDMessageHandler(HWNDMessageHandlerDelegate* delegate)
       dwm_transition_desired_(false),
       sent_window_size_changing_(false),
       left_button_down_on_caption_(false),
+      background_fullscreen_hack_(false),
       autohide_factory_(this),
       weak_factory_(this) {}
 
@@ -844,6 +845,7 @@ void HWNDMessageHandler::SetWindowIcons(const gfx::ImageSkia& window_icon,
 }
 
 void HWNDMessageHandler::SetFullscreen(bool fullscreen) {
+  set_background_fullscreen_hack(false);
   fullscreen_handler()->SetFullscreen(fullscreen);
   // If we are out of fullscreen and there was a pending DWM transition for the
   // window, then go ahead and do it now.
@@ -929,7 +931,8 @@ LRESULT HWNDMessageHandler::OnWndProc(UINT message,
   }
 
   if (message == WM_ACTIVATE && IsTopLevelWindow(window))
-    PostProcessActivateMessage(LOWORD(w_param), !!HIWORD(w_param));
+    PostProcessActivateMessage(LOWORD(w_param), !!HIWORD(w_param),
+                               reinterpret_cast<HWND>(l_param));
   return result;
 }
 
@@ -1027,12 +1030,16 @@ void HWNDMessageHandler::SetInitialFocus() {
   }
 }
 
-void HWNDMessageHandler::PostProcessActivateMessage(int activation_state,
-                                                    bool minimized) {
+void HWNDMessageHandler::PostProcessActivateMessage(
+    int activation_state,
+    bool minimized,
+    HWND window_gaining_or_losing_activation) {
   DCHECK(IsTopLevelWindow(hwnd()));
   const bool active = activation_state != WA_INACTIVE && !minimized;
-  if (delegate_->CanActivate())
-    delegate_->HandleActivationChanged(active);
+  if (delegate_->CanActivate()) {
+    delegate_->HandleActivationChanged(active,
+                                       window_gaining_or_losing_activation);
+  }
 }
 
 void HWNDMessageHandler::RestoreEnabledIfNecessary() {
@@ -2167,7 +2174,8 @@ void HWNDMessageHandler::OnWindowPosChanging(WINDOWPOS* window_pos) {
                                (work_area != last_work_area_);
       if (monitor && (monitor == last_monitor_) &&
           ((fullscreen_handler_->fullscreen() &&
-            !fullscreen_handler_->metro_snap()) ||
+            !fullscreen_handler_->metro_snap() &&
+            !background_fullscreen_hack()) ||
             work_area_changed)) {
         // A rect for the monitor we're on changed.  Normally Windows notifies
         // us about this (and thus we're reaching here due to the SetWindowPos()