Have PlatformEventObserver implementations orderly stop on destruction.

content/renderer/gamepad_shared_memory_reader.cc

 // Copyright (c) 2012 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 "content/renderer/gamepad_shared_memory_reader.h"
 
 #include "base/debug/trace_event.h"
 #include "base/metrics/histogram.h"
 #include "content/common/gamepad_hardware_buffer.h"
 #include "content/common/gamepad_user_gesture.h"
@@ skipping 87 matching lines @@
     // Clear the connected flag if the user hasn't interacted with any of the
     // gamepads to prevent fingerprinting. The actual data is not cleared.
     // WebKit will only copy out data into the JS buffers for connected
     // gamepads so this is sufficient.
     for (unsigned i = 0; i < blink::WebGamepads::itemsLengthCap; i++)
       gamepads.items[i].connected = false;
   }
 }
 
 GamepadSharedMemoryReader::~GamepadSharedMemoryReader() {
+  StopIfObserving();
 }
 
 bool GamepadSharedMemoryReader::OnControlMessageReceived(
     const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(GamepadSharedMemoryReader, message)
     IPC_MESSAGE_HANDLER(GamepadMsg_GamepadConnected, OnGamepadConnected)
     IPC_MESSAGE_HANDLER(GamepadMsg_GamepadDisconnected, OnGamepadDisconnected)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
@@ skipping 11 matching lines @@
 }
 
 void GamepadSharedMemoryReader::OnGamepadDisconnected(
     int index,
     const blink::WebGamepad& gamepad) {
   if (listener())
     listener()->didDisconnectGamepad(index, gamepad);
 }
 
 } // namespace content