[vr] Close exit prompt when clicking on background

chrome/browser/android/vr_shell/ui_scene_manager.cc

Index: chrome/browser/android/vr_shell/ui_scene_manager.cc
diff --git a/chrome/browser/android/vr_shell/ui_scene_manager.cc b/chrome/browser/android/vr_shell/ui_scene_manager.cc
index be65c923106125db36cee2fe35cf8224c597a74b..ddef836d9ccf3a6f4d0681c56296aff1b1e995d0 100644
--- a/chrome/browser/android/vr_shell/ui_scene_manager.cc
+++ b/chrome/browser/android/vr_shell/ui_scene_manager.cc
@@ -10,6 +10,7 @@
 #include "chrome/browser/android/vr_shell/textures/ui_texture.h"
 #include "chrome/browser/android/vr_shell/ui_elements/audio_capture_indicator.h"
 #include "chrome/browser/android/vr_shell/ui_elements/button.h"
+#include "chrome/browser/android/vr_shell/ui_elements/content_backplane.h"
 #include "chrome/browser/android/vr_shell/ui_elements/exit_prompt.h"
 #include "chrome/browser/android/vr_shell/ui_elements/exit_warning.h"
 #include "chrome/browser/android/vr_shell/ui_elements/loading_indicator.h"
@@ -213,7 +214,8 @@ void UiSceneManager::CreateContentQuad() {
 
   // Place an invisible but hittable plane behind the content quad, to keep the
   // reticle roughly planar with the content if near content.
-  element = base::MakeUnique<UiElement>();
+  element = base::MakeUnique<ContentBackplane>(
+      base::Bind(&UiSceneManager::OnBackplaneClicked, base::Unretained(this)));
   element->set_debug_id(kBackplane);
   element->set_id(AllocateId());
   element->set_fill(vr_shell::Fill::NONE);
@@ -457,13 +459,21 @@ void UiSceneManager::OnSecurityIconClicked() {
   ConfigureScene();
 }
 
-void UiSceneManager::OnExitPromptPrimaryButtonClicked() {
+void UiSceneManager::OnBackplaneClicked() {
+  CloseExitPrompt();
+}
+
+void UiSceneManager::CloseExitPrompt() {
   if (!scene_->is_prompting_to_exit())
     return;
   scene_->set_is_prompting_to_exit(false);
   ConfigureScene();
 }
 
+void UiSceneManager::OnExitPromptPrimaryButtonClicked() {
+  CloseExitPrompt();
+}
+
 void UiSceneManager::OnExitPromptSecondaryButtonClicked() {
   OnUnsupportedMode(UiUnsupportedMode::kUnhandledPageInfo);
 }