BoxLayout: Added set_collapse_when_hidden(), like views::Label.

ui/views/layout/box_layout_unittest.cc

Index: ui/views/layout/box_layout_unittest.cc
diff --git a/ui/views/layout/box_layout_unittest.cc b/ui/views/layout/box_layout_unittest.cc
index 59866b14d1034658a182963e4aaf351094b315a3..e2091963727ad9bfc69d5e5ab14b0478df26018c 100644
--- a/ui/views/layout/box_layout_unittest.cc
+++ b/ui/views/layout/box_layout_unittest.cc
@@ -133,6 +133,18 @@ TEST_F(BoxLayoutTest, NoSpace) {
   EXPECT_EQ(gfx::Rect(0, 0, 0, 0), childView->bounds());
 }
 
+TEST_F(BoxLayoutTest, InvisibleHost) {
+  BoxLayout* layout = new BoxLayout(BoxLayout::kHorizontal, 10, 10, 20);
+  host_->SetLayoutManager(layout);
+  host_->SetVisible(false);
+  // No collapse_when_hidden; expect full size.
+  EXPECT_EQ(gfx::Size(20, 20), layout->GetPreferredSize(host_.get()));
+
+  // Set collapse_when_hidden; expect 0x0.
+  layout->set_collapse_when_hidden(true);
+  EXPECT_EQ(gfx::Size(), layout->GetPreferredSize(host_.get()));
+}
+
 TEST_F(BoxLayoutTest, InvisibleChild) {
   BoxLayout* layout = new BoxLayout(BoxLayout::kHorizontal, 10, 10, 10);
   host_->SetLayoutManager(layout);