[sensors] Add Permission guard to the generic sensor apis.

third_party/WebKit/Source/modules/sensor/SensorProxy.cpp

 // 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 "modules/sensor/SensorProxy.h"
 
 #include "core/frame/LocalFrame.h"
+#include "modules/permissions/PermissionUtils.h"
 #include "modules/sensor/SensorProviderProxy.h"
 #include "modules/sensor/SensorReading.h"
+#include "platform/UserGestureIndicator.h"
 #include "platform/mojo/MojoHelper.h"
+#include "platform/weborigin/SecurityOrigin.h"
 #include "public/platform/Platform.h"
 
 using namespace device::mojom::blink;
 
 namespace blink {
 
+using mojom::blink::PermissionName;
+using mojom::blink::PermissionService;
+using mojom::blink::PermissionStatus;
+
 SensorProxy::SensorProxy(SensorType sensorType,
+                         PermissionService* permissionService,
+                         RefPtr<SecurityOrigin> origin,
                          SensorProviderProxy* provider,
                          std::unique_ptr<SensorReadingFactory> readingFactory)
     : m_type(sensorType),
       m_mode(ReportingMode::CONTINUOUS),
       m_provider(provider),
       m_clientBinding(this),
       m_state(SensorProxy::Uninitialized),
       m_suspended(false),
       m_readingFactory(std::move(readingFactory)),
-      m_maximumFrequency(0.0) {}
+      m_maximumFrequency(0.0),
+      m_permissionStatus(PermissionStatus::ASK),
+      m_permissionService(permissionService),
+      m_securityOrigin(std::move(origin)) {}
+
+void SensorProxy::onPermissionUpdate(PermissionStatus status) {
+  if (m_permissionStatus != status) {
+    m_permissionStatus = status;
+    if (!isInitialized())

[Mikhail, 2016/11/18 12:37:43]

so, any external permission changes could initiate initialization? initialize()
must be called only after it was initially was called from Sensor::start() (i.e.
is current state is 'initializing')

[riju_, 2016/11/21 11:23:28]

Acknowledged.

+      initialize();
+  }
+
+  // If permission is revoked, throw error.
+  if (m_permissionStatus != PermissionStatus::GRANTED)
+    handleSensorError(NotAllowedError, "Permission not granted.");

[Mikhail, 2016/11/18 12:37:42]

what it if we in the middle of initialization, or initialization is not yet
started? in second case it looks like 'onerror' will be called even before
'start' method call.

[riju_, 2016/11/21 11:23:28]

Acknowledged.

+
+  // Keep listening to changes.
+  m_permissionService->GetNextPermissionChange(
+      createPermissionDescriptor(PermissionName::SENSORS), m_securityOrigin,
+      m_permissionStatus,
+      convertToBaseCallback(WTF::bind(&SensorProxy::onPermissionUpdate,
+                                      wrapWeakPersistent(this))));
+}
 
 SensorProxy::~SensorProxy() {}
 
 void SensorProxy::dispose() {
   m_clientBinding.Close();
 }
 
 DEFINE_TRACE(SensorProxy) {
   visitor->trace(m_reading);
   visitor->trace(m_observers);
@@ skipping 11 matching lines @@
 
 void SensorProxy::initialize() {
   if (m_state != Uninitialized)
     return;
 
   if (!m_provider->sensorProvider()) {
     handleSensorError();
     return;
   }
 
-  m_state = Initializing;
   auto callback = convertToBaseCallback(
       WTF::bind(&SensorProxy::onSensorCreated, wrapWeakPersistent(this)));
-  m_provider->sensorProvider()->GetSensor(m_type, mojo::GetProxy(&m_sensor),
-                                          callback);
+
+  switch (m_permissionStatus) {
+    case PermissionStatus::ASK:
+      // Request permission.
+      m_permissionService->RequestPermission(
+          createPermissionDescriptor(PermissionName::SENSORS), m_securityOrigin,
+          UserGestureIndicator::processingUserGesture(),
+          convertToBaseCallback(WTF::bind(&SensorProxy::onPermissionUpdate,
+                                          wrapPersistent(this))));

[Mikhail, 2016/11/18 12:37:43]

why to hold proxy instance alive until onPermissionUpdate is called?

[riju_, 2016/11/21 11:23:28]

Done.

+      break;
+    case PermissionStatus::DENIED:
+      handleSensorError(NotAllowedError, "Permission not granted.");
+      break;
+    case PermissionStatus::GRANTED:
+      m_state = Initializing;
+      m_provider->sensorProvider()->GetSensor(m_type, mojo::GetProxy(&m_sensor),
+                                              callback);
+      break;
+    default:
+      NOTREACHED();
+  }
 }
 
 void SensorProxy::addConfiguration(
     SensorConfigurationPtr configuration,
     std::unique_ptr<Function<void(bool)>> callback) {
   DCHECK(isInitialized());
   m_sensor->AddConfiguration(std::move(configuration),
                              convertToBaseCallback(std::move(callback)));
 }
 
@@ skipping 128 matching lines @@
   const device::OneWriterSeqLock& seqlock = buffer->seqlock.value();
   auto version = seqlock.ReadBegin();
   auto readingData = buffer->reading;
   if (seqlock.ReadRetry(version))
     return false;
   result = readingData;
   return true;
 }
 
 }  // namespace blink