Assign names to VR UI elements for debugging and test.

chrome/browser/android/vr_shell/ui_elements.h

Index: chrome/browser/android/vr_shell/ui_elements.h
diff --git a/chrome/browser/android/vr_shell/ui_elements.h b/chrome/browser/android/vr_shell/ui_elements.h
index fc590f993bf5b8934124cacda5e507e69d7eb5a7..b020d683df5126c3ea0f607d9d6f8f141275c1e7 100644
--- a/chrome/browser/android/vr_shell/ui_elements.h
+++ b/chrome/browser/android/vr_shell/ui_elements.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_ANDROID_VR_SHELL_UI_ELEMENTS_H_
 
 #include <memory>
+#include <string>
 #include <vector>
 
 #include "base/macros.h"
@@ -97,6 +98,9 @@ struct ContentRectangle : public WorldRectangle {
   // Valid IDs are non-negative.
   int id = -1;
 
+  // Name string for debugging and testing purposes.
+  std::string name;
+
   // If a non-negative parent ID is specified, applicable transformations
   // are applied relative to the parent, rather than absolutely.
   int parent_id = -1;