[sensors] Close mock sensor stubs after test is finished

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/sensor/SensorProviderProxy.h"
 #include "platform/mojo/MojoHelper.h"
 #include "public/platform/Platform.h"
@@ skipping 102 matching lines @@
 void SensorProxy::RaiseError() {
   handleSensorError();
 }
 
 void SensorProxy::SensorReadingChanged() {
   for (Observer* observer : m_observers)
     observer->onSensorReadingChanged();
 }
 
 void SensorProxy::handleSensorError(ExceptionCode code,
-                                    const String& sanitizedMessage,
-                                    const String& unsanitizedMessage) {
+                                    String sanitizedMessage,
+                                    String unsanitizedMessage) {
   if (!Platform::current()) {
     // TODO(rockot): Remove this hack once renderer shutdown sequence is fixed.
     return;
   }
+
   m_state = Uninitialized;
+  // The m_sensor.reset() will release all callbacks and its bound parameters,
+  // therefore, handleSensorError accepts messages by value.
   m_sensor.reset();
   m_sharedBuffer.reset();
   m_sharedBufferHandle.reset();
   m_defaultConfig.reset();
   m_clientBinding.Close();
 
   for (Observer* observer : m_observers)
     observer->onSensorError(code, sanitizedMessage, unsanitizedMessage);
 }
 
@@ skipping 46 matching lines @@
   const device::OneWriterSeqLock& seqlock = buffer->seqlock.value();
   auto version = seqlock.ReadBegin();
   auto reading = buffer->reading;
   if (seqlock.ReadRetry(version))
     return false;
   m_reading = reading;
   return true;
 }
 
 }  // namespace blink