[Autofill Assistant] DetachUi when necessary to avoid race condition.

Bug: b/166266031
Change-Id: I2ab6523282c7eb271c4874abe6b4238e7ff1dffd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2375170
Commit-Queue: Clemens Arbesser <arbesser@google.com>
Reviewed-by: Luca Hunkeler <hluca@google.com>
Cr-Commit-Position: refs/heads/master@{#801718}

chrome/browser/android/autofill_assistant/client_android.cc

@@ -587,12 +587,19 @@ void ClientAndroid::InvalidateAccessToken(const std::string& access_token) {
 }
 
 void ClientAndroid::CreateController(std::unique_ptr<Service> service) {
+  if (controller_) {
+    DestroyController();
+  }
   controller_ = std::make_unique<Controller>(
       web_contents_, /* client= */ this, base::DefaultTickClock::GetInstance(),
       std::move(service));
 }
 
 void ClientAndroid::DestroyController() {
+  if (controller_ && ui_controller_android_ &&
+      ui_controller_android_->IsAttachedTo(controller_.get())) {
+    ui_controller_android_->Detach();
+  }
   controller_.reset();
   started_ = false;
 }

chrome/browser/android/autofill_assistant/ui_controller_android.cc

@@ -315,8 +315,7 @@ void UiControllerAndroid::Attach(content::WebContents* web_contents,
   client_ = client;
 
   // Detach from the current ui_delegate, if one was set previously.
-  if (ui_delegate_)
-    ui_delegate_->RemoveObserver(this);
+  Detach();
 
   // Attach to the new ui_delegate.
   ui_delegate_ = ui_delegate;
@@ -385,12 +384,17 @@ void UiControllerAndroid::Attach(content::WebContents* web_contents,
   SetVisible(true);
 }
 
+void UiControllerAndroid::Detach() {
+  if (ui_delegate_) {
+    ui_delegate_->RemoveObserver(this);
+  }
+  ui_delegate_ = nullptr;
+}
+
 UiControllerAndroid::~UiControllerAndroid() {
   Java_AutofillAssistantUiController_clearNativePtr(AttachCurrentThread(),
                                                     java_object_);
-
-  if (ui_delegate_)
-    ui_delegate_->RemoveObserver(this);
+  Detach();
 }
 
 base::android::ScopedJavaLocalRef<jobject> UiControllerAndroid::GetModel() {

chrome/browser/android/autofill_assistant/ui_controller_android.h

@@ -66,6 +66,10 @@ class UiControllerAndroid : public ControllerObserver {
               Client* client,
               UiDelegate* ui_delegate);
 
+  // Detaches the UI from |ui_delegate_|. It will stop receiving notifications
+  // from the delegate until it is attached again.
+  void Detach();
+
   // Returns true if the UI is attached to a delegate.
   bool IsAttached() { return ui_delegate_ != nullptr; }