Have PlatformEventObserver implementations orderly stop on destruction.

content/renderer/device_sensors/device_sensor_event_pump.h

 // Copyright 2014 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.
 
 #ifndef CONTENT_RENDERER_DEVICE_SENSORS_DEVICE_SENSOR_EVENT_PUMP_H_
 #define CONTENT_RENDERER_DEVICE_SENSORS_DEVICE_SENSOR_EVENT_PUMP_H_
 
 #include "base/memory/shared_memory.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
@@ skipping 38 matching lines @@
     state_ = STOPPED;
   }
 
  protected:
   explicit DeviceSensorEventPump(RenderThread* thread)
       : PlatformEventObserver<ListenerType>(thread),
         pump_delay_microseconds_(kDefaultPumpDelayMicroseconds),
         state_(STOPPED) {}
 
   virtual ~DeviceSensorEventPump() {
+    PlatformEventObserver<ListenerType>::StopIfObserving();
   }
 
   // The pump is a tri-state automaton with allowed transitions as follows:
   // STOPPED -> PENDING_START
   // PENDING_START -> RUNNING
   // PENDING_START -> STOPPED
   // RUNNING -> STOPPED
   enum PumpState {
       STOPPED,
       RUNNING,
@@ skipping 23 matching lines @@
   int pump_delay_microseconds_;
   PumpState state_;
   base::RepeatingTimer<DeviceSensorEventPump> timer_;
 
   DISALLOW_COPY_AND_ASSIGN(DeviceSensorEventPump);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_DEVICE_SENSORS_DEVICE_SENSOR_EVENT_PUMP_H_