MessageBubble which does not require separate window and does not grab input on mouse press event.

views/widget/widget_gtk.cc

Index: views/widget/widget_gtk.cc
diff --git a/views/widget/widget_gtk.cc b/views/widget/widget_gtk.cc
index 78137c5c472a4d3cd43c71683149d4ec064fcbc1..5d946f55d83f50229307176fe6337fce8cde88e1 100644
--- a/views/widget/widget_gtk.cc
+++ b/views/widget/widget_gtk.cc
@@ -1153,6 +1153,15 @@ void WidgetGtk::ReleaseGrab() {
   }
 }
 
+void WidgetGtk::HandleGrabBroke() {
+  if (has_capture_) {
+    if (is_mouse_down_)
+      root_view_->ProcessMouseDragCanceled();
+    is_mouse_down_ = false;
+    has_capture_ = false;
+  }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // WidgetGtk, private:
 
@@ -1399,15 +1408,6 @@ void WidgetGtk::ConfigureWidgetForIgnoreEvents() {
       0);
 }
 
-void WidgetGtk::HandleGrabBroke() {
-  if (has_capture_) {
-    if (is_mouse_down_)
-      root_view_->ProcessMouseDragCanceled();
-    is_mouse_down_ = false;
-    has_capture_ = false;
-  }
-}
-
 void WidgetGtk::DrawTransparentBackground(GtkWidget* widget,
                                           GdkEventExpose* event) {
   cairo_t* cr = gdk_cairo_create(widget->window);