Tentatively goes into WebVR presentation mode if page listens to vrdisplayactivate.

chrome/browser/android/vr_shell/vr_shell_delegate.cc

Index: chrome/browser/android/vr_shell/vr_shell_delegate.cc
diff --git a/chrome/browser/android/vr_shell/vr_shell_delegate.cc b/chrome/browser/android/vr_shell/vr_shell_delegate.cc
index 297168ddc871d13c21ac8d13006880b175f2133c..70daa50b10b366d2c1c2b5ce7fe329be20fb0c4e 100644
--- a/chrome/browser/android/vr_shell/vr_shell_delegate.cc
+++ b/chrome/browser/android/vr_shell/vr_shell_delegate.cc
@@ -19,7 +19,8 @@ using base::android::AttachCurrentThread;
 
 namespace vr_shell {
 
-VrShellDelegate::VrShellDelegate(JNIEnv* env, jobject obj) {
+VrShellDelegate::VrShellDelegate(JNIEnv* env, jobject obj)
+    : weak_ptr_factory_(this) {
   DVLOG(1) << __FUNCTION__ << "=" << this;
   j_vr_shell_delegate_.Reset(env, obj);
 }
@@ -107,7 +108,9 @@ void VrShellDelegate::DisplayActivate(JNIEnv* env,
                                       const JavaParamRef<jobject>& obj) {
   if (device_provider_) {
     device_provider_->Device()->OnActivate(
-        device::mojom::VRDisplayEventReason::MOUNTED);
+        device::mojom::VRDisplayEventReason::MOUNTED,
+        base::Bind(&VrShellDelegate::OnActivateDisplayHandled,
+                   weak_ptr_factory_.GetWeakPtr()));
   }
 }
 
@@ -203,6 +206,14 @@ void VrShellDelegate::CreateNonPresentingDelegate() {
                                                 interval_seconds_);
 }
 
+void VrShellDelegate::OnActivateDisplayHandled(bool present_requested) {
+  if (!present_requested) {
+    // WebVR page didn't request presentation in the vrdisplayactivate handler.
+    // Tell VrShell that we are in VR Browsing Mode.
+    ExitWebVRPresent();
+  }
+}
+
 device::GvrDelegate* VrShellDelegate::GetDelegate() {
   if (presenting_delegate_)
     return presenting_delegate_;