[M101-merge] assistant: Speculative fix of card element view

We suspect that when ui_element is added, the contents_view is nullptr.
Add a check before creating the card element view.
We still need to investigate why the ui_element could be added multiple
times or why the contents_view is nullptr. Will track in b/228109139

Bug: 1303227
Test: NA

(cherry picked from commit f996270)

Change-Id: I573418dc04567756362bb765e2715ea7b0e41530
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3573689
Reviewed-by: Eric Sum <esum@google.com>
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: Tao Wu <wutao@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#989684}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3588959
Cr-Commit-Position: refs/branch-heads/4951@{#791}
Cr-Branched-From: 27de622-refs/heads/main@{#982481}

ash/assistant/model/ui/assistant_card_element.cc

@@ -95,6 +95,10 @@ void AssistantCardElement::Process(ProcessingCallback callback) {
   processor_->Process();
 }
 
+bool AssistantCardElement::has_contents_view() const {
+  return !!contents_view_;
+}
+
 bool AssistantCardElement::Compare(const AssistantUiElement& other) const {
   return other.type() == AssistantUiElementType::kCard &&
          static_cast<const AssistantCardElement&>(other).html() == html_;

ash/assistant/model/ui/assistant_card_element.h

@@ -30,6 +30,7 @@ class COMPONENT_EXPORT(ASSISTANT_MODEL) AssistantCardElement
   // AssistantUiElement:
   void Process(ProcessingCallback callback) override;
 
+  bool has_contents_view() const;
   const std::string& html() const { return html_; }
   const std::string& fallback() const { return fallback_; }
   std::unique_ptr<AshWebView> MoveContentsView() {

ash/assistant/ui/main_stage/assistant_ui_element_view_factory.cc

@@ -13,6 +13,7 @@
 #include "ash/assistant/ui/main_stage/assistant_error_element_view.h"
 #include "ash/assistant/ui/main_stage/assistant_text_element_view.h"
 #include "ash/assistant/ui/main_stage/assistant_ui_element_view.h"
+#include "base/logging.h"
 
 namespace ash {
 
@@ -25,9 +26,17 @@ AssistantUiElementViewFactory::~AssistantUiElementViewFactory() = default;
 std::unique_ptr<AssistantUiElementView> AssistantUiElementViewFactory::Create(
     const AssistantUiElement* ui_element) const {
   switch (ui_element->type()) {
-    case AssistantUiElementType::kCard:
-      return std::make_unique<AssistantCardElementView>(
-          delegate_, static_cast<const AssistantCardElement*>(ui_element));
+    case AssistantUiElementType::kCard: {
+      auto* card_element = static_cast<const AssistantCardElement*>(ui_element);
+      if (!card_element->has_contents_view()) {
+        // TODO(b/228109139): Find the root cause why reaches here.
+        LOG(DFATAL) << "AssistantCardElement has null contents_view. Not "
+                       "create the view.";
+        return nullptr;
+      }
+      return std::make_unique<AssistantCardElementView>(delegate_,
+                                                        card_element);
+    }
     case AssistantUiElementType::kError:
       return std::make_unique<AssistantErrorElementView>(
           static_cast<const AssistantErrorElement*>(ui_element));

ash/assistant/ui/main_stage/ui_element_container_view.cc

@@ -206,6 +206,9 @@ std::unique_ptr<ElementAnimator> UiElementContainerView::HandleUiElement(
     const AssistantUiElement* ui_element) {
   // Create a new view for the |ui_element|.
   auto view = view_factory_->Create(ui_element);
+  if (!view) {
+    return nullptr;
+  }
 
   // If the first UI element is a card, it has a unique margin requirement.
   const bool is_card = ui_element->type() == AssistantUiElementType::kCard;