Add way to get native VR UI information from Java

chrome/browser/android/vr_shell/vr_shell.cc

Index: chrome/browser/android/vr_shell/vr_shell.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell.cc b/chrome/browser/android/vr_shell/vr_shell.cc
index edcbb68f0fe05e2c0f75e96229e281b9e33a5b32..6fe614e7092290851334de23d846d14e6d92582a 100644
--- a/chrome/browser/android/vr_shell/vr_shell.cc
+++ b/chrome/browser/android/vr_shell/vr_shell.cc
@@ -9,7 +9,9 @@
 #include <string>
 #include <utility>
 
+#include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
+#include "base/json/json_writer.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/threading/platform_thread.h"
@@ -397,6 +399,19 @@ void VrShell::SetHistoryButtonsEnabled(JNIEnv* env,
   html_interface_->SetHistoryButtonsEnabled(can_go_back, can_go_forward);
 }
 
+void VrShell::RequestUiElementInfo(JNIEnv* env,
+                                   const JavaParamRef<jobject>& obj,
+                                   jintArray element_ids,
+                                   jint callback_id) {
+  std::vector<int> element_ids_vector;
+  base::android::JavaIntArrayToIntVector(env, element_ids, &element_ids_vector);
+  PostToGlThreadWhenReady(
+      base::Bind(&VrShellGl::CreateUiElementInfos, gl_thread_->GetVrShellGl(),
+                 element_ids_vector, callback_id,
+                 base::Bind(&VrShell::OnUiElementInfoCreated,
+                            weak_ptr_factory_.GetWeakPtr())));
+}
+
 void VrShell::UiSurfaceChanged(jobject surface) {
   ui_compositor_->SurfaceChanged(surface);
 }
@@ -539,6 +554,17 @@ void VrShell::DoUiAction(const UiAction action,
   }
 }
 
+void VrShell::OnUiElementInfoCreated(
+    int callback_id,
+    std::unique_ptr<base::DictionaryValue> info) {
+  std::string json_reply;
+  base::JSONWriter::Write(*info, &json_reply);

[bsheedy, 2017/03/24 18:47:54]

Converting to a JSON string in native then back to an object in Java doesn't
seem like the ideal approach, but I'm not aware of a better way to get a
base::Value type back to Java.

[tiborg, 2017/03/27 15:14:33]

I'm not aware of a better solution either. I think it is suitable for testing.

+  JNIEnv* env = base::android::AttachCurrentThread();
+  Java_VrShellImpl_replyToUiElementInfoRequest(
+      env, j_vr_shell_.obj(),
+      base::android::ConvertUTF8ToJavaString(env, json_reply), callback_id);
+}
+
 void VrShell::RenderViewHostChanged(content::RenderViewHost* old_host,
                                     content::RenderViewHost* new_host) {
   content::RenderWidgetHostView* view = new_host->GetWidget()->GetView();