Implement a means of letting native VR Shell control the HTML UI.

chrome/browser/android/vr_shell/ui_interface.cc

Index: chrome/browser/android/vr_shell/ui_interface.cc
diff --git a/chrome/browser/android/vr_shell/ui_interface.cc b/chrome/browser/android/vr_shell/ui_interface.cc
new file mode 100644
index 0000000000000000000000000000000000000000..640e3f7f36e0d7392321fb540905dc05cd18a522
--- /dev/null
+++ b/chrome/browser/android/vr_shell/ui_interface.cc
@@ -0,0 +1,46 @@
+// 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.
+
+#include "chrome/browser/android/vr_shell/ui_interface.h"
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"

[bshe, 2016/10/19 21:02:40]

nit: remove the above two header as you included in .h already

[cjgrant, 2016/10/20 15:25:39]

Done.

+#include "chrome/browser/ui/webui/vr_shell/vr_shell_ui_message_handler.h"
+
+namespace vr_shell {
+
+UiInterface::UiInterface() {
+  SetMode(Mode::STANDARD);
+}
+
+UiInterface::~UiInterface() {}
+
+void UiInterface::SetUiMessageHandler(
+    base::WeakPtr<VrShellUIMessageHandler> handler) {
+  handler_ = handler;
+}
+
+void UiInterface::SetMode(Mode mode) {
+  updates_.SetInteger("mode", static_cast<int>(mode));

[mthiesse, 2016/10/19 18:04:10]

Maybe store the mode we're in locally, and only update on change? This class
could manage the shared state between UI and backend.

[cjgrant, 2016/10/20 15:25:38]

Possibly, but at this point we shouldn't get a mode set more than once per page,
and some things we need to send even if they don't change (secure origin calls
should restart the 30-second temporary warning timer).  Will certainly cache
state in the future if we need to.

+  FlushUpdates();
+}
+
+void UiInterface::SetSecureOrigin(bool secure) {
+  updates_.SetBoolean("secureOrigin", static_cast<int>(secure));

[mthiesse, 2016/10/19 18:04:10]

Same comment here, you can store whether we're in secure origin mode locally and
only update on change.

[cjgrant, 2016/10/20 15:25:39]

See above.

+  FlushUpdates();
+}
+
+void UiInterface::OnDomContentsLoaded() {
+  loaded_ = true;
+  FlushUpdates();
+}
+
+void UiInterface::FlushUpdates() {
+  if (loaded_ && handler_) {
+    handler_->GetWebUi()->CallJavascriptFunctionUnsafe(

[bshe, 2016/10/19 21:02:40]

Calling "CallJavascriptFunctionUnsafe" directly is discouraged. Perhaps you can
create a public function in vr_shell_ui_message_handler.cc and wrap
WebUiMessageHanlder:CallJavascriptFunction in it. This way, you don't need to
check |loaded_| too.  Unless there is a case that you might try to call js
before webui is ready.

[cjgrant, 2016/10/20 14:32:40]

As of now, VrShell gets calls to set the mode to WebVR before we see
OnDomContentsLoaded().  So there needs to be some caching of this state, such
that when we see the HTML UI finish loading, we can push any accumulated
information up to it.

Interestingly, for secure origin, I think we actually want to relay calls to the
HTML UI every time VR shell gets this call.  If we go from insecure site to
insecure site, the HTML UI should know so that it can restart the temporary
warning timer.

I'll think about this a bit more...

[cjgrant, 2016/10/20 15:25:38]

Done.

+        "chrome.vrShellUi.command", updates_);
+  }
+}
+
+}  // namespace vr_shell