Fix getting notified twice after subscribe to notifications and call readValue

device/bluetooth/bluez/bluetooth_remote_gatt_service_bluez.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 <iterator>
 
 #include "base/logging.h"
 #include "dbus/property.h"
 #include "device/bluetooth/bluez/bluetooth_adapter_bluez.h"
 #include "device/bluetooth/bluez/bluetooth_device_bluez.h"
@@ skipping 225 matching lines @@
   bluez::BluetoothGattCharacteristicClient::Properties* properties =
       bluez::BluezDBusManager::Get()
           ->GetBluetoothGattCharacteristicClient()
           ->GetProperties(object_path);
 
   DCHECK(properties);
   DCHECK(GetAdapter());
 
   if (property_name == properties->flags.name())
     NotifyServiceChanged();
-  else if (property_name == properties->value.name())
-    GetAdapter()->NotifyGattCharacteristicValueChanged(
-        iter->second, properties->value.value());
+  else if (property_name == properties->value.name()) {
+    DCHECK_GE(iter->second->num_of_characteristic_value_read_in_progress_, 0);
+    if (iter->second->num_of_characteristic_value_read_in_progress_ > 0) {
+      --iter->second->num_of_characteristic_value_read_in_progress_;
+    } else {
+      GetAdapter()->NotifyGattCharacteristicValueChanged(
+          iter->second, properties->value.value());
+    }
+  }
 }
 
 }  // namespace bluez