views: Forward declare "class View;" in layout_manager.h

views/layout/box_layout.cc

Index: views/layout/box_layout.cc
diff --git a/views/layout/box_layout.cc b/views/layout/box_layout.cc
index 5025d7ebc5516a4d225a595d2ee9b4cde6e0b9a7..6a6ede6c93918130d53672859e48069caa0906f4 100644
--- a/views/layout/box_layout.cc
+++ b/views/layout/box_layout.cc
@@ -4,6 +4,10 @@
 
 #include "views/layout/box_layout.h"
 
+#include "gfx/insets.h"
+#include "gfx/rect.h"
+#include "views/view.h"
+
 namespace views {
 
 BoxLayout::BoxLayout(BoxLayout::Orientation orientation,
@@ -16,6 +20,9 @@ BoxLayout::BoxLayout(BoxLayout::Orientation orientation,
       between_child_spacing_(between_child_spacing) {
 }
 
+BoxLayout::~BoxLayout() {
+}
+
 void BoxLayout::Layout(View* host) {
   gfx::Rect childArea(gfx::Rect(host->size()));
   childArea.Inset(host->GetInsets());