Add way to get native VR UI information from Java

chrome/browser/android/vr_shell/ui_scene.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_ANDROID_VR_SHELL_UI_SCENE_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_UI_SCENE_H_
 
 #include <memory>
+#include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "chrome/browser/android/vr_shell/vr_math.h"
 
 namespace base {
 class DictionaryValue;
 class ListValue;
 }
 
@@ skipping 41 matching lines @@
   // unit used in animations.
   void UpdateTransforms(int64_t time_in_micro);
 
   // Handle a batch of commands passed from the UI HTML.
   void HandleCommands(std::unique_ptr<base::ListValue> commands,
                       int64_t time_in_micro);
 
   const std::vector<std::unique_ptr<ContentRectangle>>& GetUiElements() const;
 
   ContentRectangle* GetUiElementById(int element_id);
+  ContentRectangle* GetUiElementByName(const std::string& element_name);
 
   std::vector<const ContentRectangle*> GetWorldElements() const;
   std::vector<const ContentRectangle*> GetHeadLockedElements() const;
   bool HasVisibleHeadLockedElements() const;
 
   const Colorf& GetBackgroundColor() const;
   float GetBackgroundDistance() const;
   bool GetWebVrRenderingEnabled() const;
 
+  // For testing whether the native state matches expectations

[cjgrant, 2017/03/30 14:48:35]

- Needs a period (all comments need to be full sentences as per style guide).
- Sorry to be picky, but could you further elaborate?  Something like "Builds a
dictionary of UI element properties for testing purposes. The dictionary can be
serialized and passed to Java in end-to-end tests."  Or something.

[bsheedy, 2017/03/30 21:05:14]

Done.

+  std::unique_ptr<base::DictionaryValue> CreateUiElementInfo(
+      std::string element_name);

[cjgrant, 2017/03/30 14:48:36]

const std::string& here too.  Could you scrub the rest of the CL and make sure
none are missed?  In general, any time you're passing an object for read-only
purposes, you want to do it as a const reference.  The style guide points out
that if you'll modify the object it should be passed through a pointer instead,
but that doesn't matter here.  

[bsheedy, 2017/03/30 21:05:14]

Done, found one additional place where const ref could be used (callback to the
main thread).

+
  private:
   void ApplyRecursiveTransforms(ContentRectangle* element);
   void ApplyDictToElement(const base::DictionaryValue& dict,
                           ContentRectangle* element);
 
   std::vector<std::unique_ptr<ContentRectangle>> ui_elements_;
   ContentRectangle* content_element_ = nullptr;
   Colorf background_color_ = {0.1f, 0.1f, 0.1f, 1.0f};
   float background_distance_ = 10.0f;
   bool webvr_rendering_enabled_ = true;
 
   DISALLOW_COPY_AND_ASSIGN(UiScene);
 };
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_SCENE_H_