Tie VR omnibox to page load progress through TabObserver.

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 ee4aa9843e6188d468b450677340af9e5b586d8b..fbe9cde45a4864b7b532e12981c65458e748f0a3 100644
--- a/chrome/browser/android/vr_shell/vr_shell.cc
+++ b/chrome/browser/android/vr_shell/vr_shell.cc
@@ -268,6 +268,13 @@ void VrShell::SetWebVrMode(JNIEnv* env,
   }
 }
 
+void VrShell::OnLoadProgressChanged(
+    JNIEnv* env,
+    const base::android::JavaParamRef<jobject>& obj,
+    double progress) {
+  html_interface_->SetLoadProgress(progress);
+}
+
 void VrShell::SetGvrPoseForWebVr(const gvr::Mat4f& pose, uint32_t pose_num) {
   GLThread* thread = static_cast<GLThread*>(gl_thread_.get());
   if (thread->IsRunning()) {