Clean up WebVR RequestPresent and make callback asynchronous.

chrome/browser/android/vr_shell/vr_shell_delegate.cc

 // 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/vr_shell_delegate.h"
 
 #include "base/android/jni_android.h"
 #include "chrome/browser/android/vr_shell/vr_shell.h"
 #include "device/vr/android/gvr/gvr_device_provider.h"
 #include "jni/VrShellDelegate_jni.h"
@@ skipping 49 matching lines @@
   return device_provider_;
 }
 
 void VrShellDelegate::ExitWebVRIfNecessary(JNIEnv* env, jobject obj) {
   if (!device_provider_)
     return;
 
   device_provider_->OnGvrDelegateRemoved();
 }
 
-bool VrShellDelegate::RequestWebVRPresent(
-    base::WeakPtr<device::GvrDeviceProvider> device_provider) {
-  // Only set one device provider at a time
+void VrShellDelegate::SetPresentResult(JNIEnv* env, jobject obj,
+                                       jboolean result) {
+  CHECK(!present_callback_.is_null());
+  present_callback_.Run(result);
+  present_callback_.Reset();
+}
+
+void VrShellDelegate::RequestWebVRPresent(
+    base::WeakPtr<device::GvrDeviceProvider> device_provider,
+    const base::Callback<void(bool)>& callback) {
+  if (!present_callback_.is_null()) {
+    // Can only handle one request at a time. This is also extremely unlikely to
+    // happen in practice.
+    callback.Run(false);
+  }
+  // Only set one device provider at a time.
   DCHECK(!device_provider_);
+
   device_provider_ = device_provider;
+  present_callback_ = callback;
 
-  // If/When VRShell is ready for use it will call OnVrShellReady.
+  // If/When VRShell is ready for use it will call SetPresentResult.
   JNIEnv* env = AttachCurrentThread();
-  Java_VrShellDelegate_enterVRIfNecessary(env, j_vr_shell_delegate_.obj(),
-                                          true);
-  return true;
+  Java_VrShellDelegate_presentRequested(env, j_vr_shell_delegate_.obj(), true);
 }
 
 void VrShellDelegate::ExitWebVRPresent() {
   device_provider_.reset();
 
   // VRShell is no longer needed by WebVR, allow it to shut down if it's not
   // being used elsewhere.
   JNIEnv* env = AttachCurrentThread();
   Java_VrShellDelegate_exitWebVR(env, j_vr_shell_delegate_.obj());
 }
@@ skipping 27 matching lines @@
 
 bool RegisterVrShellDelegate(JNIEnv* env) {
   return RegisterNativesImpl(env);
 }
 
 jlong Init(JNIEnv* env, const JavaParamRef<jobject>& obj) {
   return reinterpret_cast<intptr_t>(new VrShellDelegate(env, obj));
 }
 
 }  // namespace vr_shell