Fix flicker on tab switch on chromeos.

views/controls/native/native_view_host_gtk.cc

Index: views/controls/native/native_view_host_gtk.cc
diff --git a/views/controls/native/native_view_host_gtk.cc b/views/controls/native/native_view_host_gtk.cc
index 50255f916e604dbe4401b9e1d460155c4fe99233..1290752dd80fd38a9ed8f51d2bf0b5c51679eb05 100644
--- a/views/controls/native/native_view_host_gtk.cc
+++ b/views/controls/native/native_view_host_gtk.cc
@@ -85,6 +85,11 @@ void UnblockFocusSignals(GtkWidget* widget, gpointer data) {
     gtk_container_foreach(GTK_CONTAINER(widget), UnblockFocusSignals, data);
 }
 
+// Removes |child| from |parent|.
+void RemoveFromParent(GtkWidget* child, gpointer parent) {
+  gtk_container_remove(GTK_CONTAINER(parent), child);
+}
+
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -100,31 +105,31 @@ NativeViewHostGtk::NativeViewHostGtk(NativeViewHost* host)
 }
 
 NativeViewHostGtk::~NativeViewHostGtk() {
-  if (fixed_)
+  if (fixed_) {
+    gtk_container_foreach(GTK_CONTAINER(fixed_), RemoveFromParent, fixed_);
     gtk_widget_destroy(fixed_);
+  }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeViewHostGtk, NativeViewHostWrapper implementation:
 
 void NativeViewHostGtk::NativeViewAttached() {
-  DCHECK(host_->native_view());
-  if (gtk_widget_get_parent(host_->native_view()))
-    gtk_widget_reparent(host_->native_view(), fixed_);
-  else
-    gtk_container_add(GTK_CONTAINER(fixed_), host_->native_view());
+  AttachHostWidget();
+
+  GtkWidget* host_widget = host_->native_view();
 
   // Let the widget know that the native component has been painted.
-  views::NativeWidgetGtk::RegisterChildExposeHandler(host_->native_view());
+  views::NativeWidgetGtk::RegisterChildExposeHandler(host_widget);
 
   if (!destroy_signal_id_) {
-    destroy_signal_id_ = g_signal_connect(host_->native_view(),
+    destroy_signal_id_ = g_signal_connect(host_widget,
                                           "destroy", G_CALLBACK(CallDestroy),
                                           this);
   }
 
   if (!focus_signal_id_) {
-    focus_signal_id_ = g_signal_connect(host_->native_view(),
+    focus_signal_id_ = g_signal_connect(host_widget,
                                         "focus-in-event",
                                         G_CALLBACK(CallFocusIn), this);
   }
@@ -132,35 +137,20 @@ void NativeViewHostGtk::NativeViewAttached() {
   // Always layout though.
   host_->Layout();
 
-  // We own the native view as long as it's attached, so that we can safely
-  // reparent it in multiple passes.
-  gtk_widget_ref(host_->native_view());
-
   // TODO(port): figure out focus.
 }
 
 void NativeViewHostGtk::NativeViewDetaching(bool destroyed) {
-  DCHECK(host_->native_view());
+  GtkWidget* host_widget = host_->native_view();
+  DCHECK(host_widget);
 
-  g_signal_handler_disconnect(G_OBJECT(host_->native_view()),
-                              destroy_signal_id_);
+  g_signal_handler_disconnect(G_OBJECT(host_widget), destroy_signal_id_);
   destroy_signal_id_ = 0;
 
-  g_signal_handler_disconnect(G_OBJECT(host_->native_view()),
-                              focus_signal_id_);
+  g_signal_handler_disconnect(G_OBJECT(host_widget), focus_signal_id_);
   focus_signal_id_ = 0;
 
   installed_clip_ = false;
-
-  if (fixed_ && !destroyed) {
-    DCHECK_NE(static_cast<gfx::NativeView>(NULL),
-              gtk_widget_get_parent(host_->native_view()));
-    gtk_container_remove(GTK_CONTAINER(fixed_), host_->native_view());
-    DCHECK_EQ(
-        0U, g_list_length(gtk_container_get_children(GTK_CONTAINER(fixed_))));
-  }
-
-  g_object_unref(G_OBJECT(host_->native_view()));
 }
 
 void NativeViewHostGtk::AddedToWidget() {
@@ -174,15 +164,14 @@ void NativeViewHostGtk::AddedToWidget() {
   if (!host_->native_view())
     return;
 
-  if (gtk_widget_get_parent(host_->native_view()))
-    gtk_widget_reparent(host_->native_view(), fixed_);
-  else
-    gtk_container_add(GTK_CONTAINER(fixed_), host_->native_view());
+  AttachHostWidget();
 
-  if (host_->IsVisibleInRootView())
+  if (host_->IsVisibleInRootView()) {
+    gtk_widget_show(host_->native_view());
     gtk_widget_show(fixed_);
-  else
+  } else {
     gtk_widget_hide(fixed_);
+  }
   host_->Layout();
 }
 
@@ -235,18 +224,19 @@ void NativeViewHostGtk::ShowWidget(int x, int y, int w, int h) {
     fixed_h = std::min(installed_clip_bounds_.height(), h);
   }
 
+  GtkWidget* host_widget = host_->native_view();
   // Don't call gtk_widget_size_allocate now, as we're possibly in the
   // middle of a re-size, and it kicks off another re-size, and you
   // get flashing.  Instead, we'll set the desired size as properties
   // on the widget and queue the re-size.
-  gtk_views_fixed_set_widget_size(host_->native_view(), child_w, child_h);
-  gtk_fixed_move(GTK_FIXED(fixed_), host_->native_view(), child_x, child_y);
+  gtk_views_fixed_set_widget_size(host_widget, child_w, child_h);
+  gtk_fixed_move(GTK_FIXED(fixed_), host_widget, child_x, child_y);
 
   // Size and place the fixed_.
   GetHostWidget()->PositionChild(fixed_, fixed_x, fixed_y, fixed_w, fixed_h);
 
+  gtk_widget_show(host_widget);
   gtk_widget_show(fixed_);
-  gtk_widget_show(host_->native_view());
 }
 
 void NativeViewHostGtk::HideWidget() {
@@ -255,8 +245,9 @@ void NativeViewHostGtk::HideWidget() {
 }
 
 void NativeViewHostGtk::SetFocus() {
-  DCHECK(host_->native_view());
-  gtk_widget_grab_focus(host_->native_view());
+  GtkWidget* host_widget = host_->native_view();
+  DCHECK(host_widget);
+  gtk_widget_grab_focus(host_widget);
 }
 
 gfx::NativeViewAccessible NativeViewHostGtk::GetNativeViewAccessible() {
@@ -290,19 +281,24 @@ void NativeViewHostGtk::CreateFixed(bool needs_window) {
   fixed_ = gtk_views_fixed_new();
   gtk_widget_set_name(fixed_, "views-native-view-host-fixed");
   gtk_fixed_set_has_window(GTK_FIXED(fixed_), needs_window);
+
   // Defeat refcounting. We need to own the fixed.
   gtk_widget_ref(fixed_);
 
   NativeWidgetGtk* widget_gtk = GetHostWidget();
-  if (widget_gtk)
+  if (widget_gtk) {
     widget_gtk->AddChild(fixed_);
+    // Clear the background so we don't get flicker.
+    gtk_widget_realize(fixed_);
+    gdk_window_set_back_pixmap(fixed_->window, NULL, false);
+  }
 
   if (host_->native_view())
-    gtk_container_add(GTK_CONTAINER(fixed_), host_->native_view());
+    AttachHostWidget();
 
-  if (widget_gtk && host_->native_view() && focused_widget) {
+  if (widget_gtk && host_->native_view() && focused_widget)
     gtk_widget_grab_focus(focused_widget);
-  }
+
   if (focus_event_blocked) {
     // Unblocking a signal handler that is not blocked fails.
     // Unblock only when it's unblocked.
@@ -315,13 +311,9 @@ void NativeViewHostGtk::DestroyFixed() {
     return;
 
   gtk_widget_hide(fixed_);
+  gtk_container_foreach(GTK_CONTAINER(fixed_), RemoveFromParent, fixed_);
   GetHostWidget()->RemoveChild(fixed_);
 
-  if (host_->native_view()) {
-    // We can safely remove the widget from its container since we own the
-    // widget from the moment it is attached.
-    gtk_container_remove(GTK_CONTAINER(fixed_), host_->native_view());
-  }
   // fixed_ should not have any children this point.
   DCHECK_EQ(0U,
             g_list_length(gtk_container_get_children(GTK_CONTAINER(fixed_))));
@@ -349,6 +341,30 @@ GtkWidget* NativeViewHostGtk::GetFocusedDescendant() {
       focused : NULL;
 }
 
+void NativeViewHostGtk::AttachHostWidget() {
+  GtkWidget* host_widget = host_->native_view();
+  DCHECK(host_widget);
+
+  GtkWidget* host_parent = gtk_widget_get_parent(host_widget);
+  bool parent_changed = true;
+  if (host_parent) {
+    if (host_parent != fixed_)
+      gtk_widget_reparent(host_widget, fixed_);
+    else
+      parent_changed = false;
+  } else {
+    gtk_container_add(GTK_CONTAINER(fixed_), host_widget);
+  }
+
+  if (parent_changed) {
+    // We need to clear the background so we don't get flicker on tab switching.
+    // To do that we must realize the widget if it's not already.
+    if (!GTK_WIDGET_REALIZED(host_widget))
+      gtk_widget_realize(host_widget);
+    gdk_window_set_back_pixmap(host_widget->window, NULL, false);
+  }
+}
+
 // static
 void NativeViewHostGtk::CallDestroy(GtkObject* object,
                                     NativeViewHostGtk* host) {