Add top margin to first card in UiElementContainerView.

Per the spec, the first card element should have a top margin of 40dip.

See bug for spec/screenshots.

Bug: b:113611382
Change-Id: I323bc7283db600e1f1e319652715b572583a6fbe
Reviewed-on: https://chromium-review.googlesource.com/1185878Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#587911}

ash/assistant/ui/main_stage/ui_element_container_view.cc

@@ -26,6 +26,7 @@
 #include "ui/events/event.h"
 #include "ui/events/event_sink.h"
 #include "ui/events/event_utils.h"
+#include "ui/views/border.h"
 #include "ui/views/controls/native/native_view_host.h"
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/fill_layout.h"
@@ -37,6 +38,7 @@ namespace ash {
 namespace {
 
 // Appearance.
+constexpr int kFirstCardMarginTopDip = 40;
 constexpr int kPaddingHorizontalDip = 32;
 
 // Card element animation.
@@ -160,8 +162,17 @@ class CardElementViewHolder : public views::NativeViewHost,
 
   // views::ViewObserver:
   void OnViewPreferredSizeChanged(views::View* view) override {
-    contents_view_->SetPreferredSize(view->GetPreferredSize());
-    SetPreferredSize(view->GetPreferredSize());
+    gfx::Size preferred_size = view->GetPreferredSize();
+
+    if (border()) {
+      // When a border is present we need to explicitly account for it in our
+      // size calculations by enlarging our preferred size by the border insets.
+      const gfx::Insets insets = border()->GetInsets();
+      preferred_size.Enlarge(insets.width(), insets.height());
+    }
+
+    contents_view_->SetPreferredSize(preferred_size);
+    SetPreferredSize(preferred_size);
   }
 
   void Attach() {
@@ -303,6 +314,9 @@ void UiElementContainerView::OnResponseCleared() {
   // We can clear any pending UI elements as they are no longer relevant.
   pending_ui_element_list_.clear();
   SetProcessingUiElement(false);
+
+  // Reset state for the next response.
+  is_first_card_ = true;
 }
 
 void UiElementContainerView::OnResponseAdded(
@@ -433,6 +447,20 @@ void UiElementContainerView::OnCardReady(
         app_list::AnswerCardContentsRegistry::Get()->GetView(
             embed_token.value()));
 
+    if (is_first_card_) {
+      is_first_card_ = false;
+
+      // The first card requires a top margin of |kFirstCardMarginTopDip|, but
+      // we need to account for child spacing because the first card is not
+      // necessarily the first UI element.
+      const int top_margin_dip = child_count() == 0
+                                     ? kFirstCardMarginTopDip
+                                     : kFirstCardMarginTopDip - kSpacingDip;
+
+      // We effectively create a top margin by applying an empty border.
+      view_holder->SetBorder(views::CreateEmptyBorder(top_margin_dip, 0, 0, 0));
+    }
+
     content_view()->AddChildView(view_holder);
     view_holder->Attach();
 

ash/assistant/ui/main_stage/ui_element_container_view.h

@@ -88,6 +88,10 @@ class UiElementContainerView : public AssistantScrollView,
   std::unique_ptr<ui::CallbackLayerAnimationObserver>
       ui_elements_exit_animation_observer_;
 
+  // Whether or not the card we are adding is the first card for the current
+  // Assistant response. The first card requires the addition of a top margin.
+  bool is_first_card_ = true;
+
   // Weak pointer factory used for card rendering requests.
   base::WeakPtrFactory<UiElementContainerView> render_request_weak_factory_;