Fix getting notified twice after subscribe to notifications and call readValue

device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm

 // 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 "device/bluetooth/bluetooth_remote_gatt_characteristic_mac.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 239 matching lines @@
     characteristic_value_read_or_write_in_progress_ = false;
     if (error) {
       VLOG(1) << "Bluetooth error while reading for characteristic, domain: "
               << base::SysNSStringToUTF8(error.domain)
               << ", error code: " << error.code;
       BluetoothGattService::GattErrorCode error_code =
           BluetoothDeviceMac::GetGattErrorCodeFromNSError(error);
       callbacks.second.Run(error_code);
       return;
     }
-    UpdateValueAndNotify();
+    UpdateValue();
     callbacks.first.Run(value_);
   } else if (IsNotifying()) {
-    UpdateValueAndNotify();
+    UpdateValue();
+    gatt_service_->GetMacAdapter()->NotifyGattCharacteristicValueChanged(
+        this, value_);
   } else {
     // In case of buggy device, nothing should be done if receiving extra
     // read confirmation.
     VLOG(1) << "Characteristic value updated while having no pending read nor "
                "notification.";
   }
 }
 
-void BluetoothRemoteGattCharacteristicMac::UpdateValueAndNotify() {
+void BluetoothRemoteGattCharacteristicMac::UpdateValue() {
   NSData* nsdata_value = cb_characteristic_.get().value;
   const uint8_t* buffer = static_cast<const uint8_t*>(nsdata_value.bytes);
   value_.assign(buffer, buffer + nsdata_value.length);
-  gatt_service_->GetMacAdapter()->NotifyGattCharacteristicValueChanged(this,
-                                                                       value_);
 }
 
 void BluetoothRemoteGattCharacteristicMac::DidWriteValue(NSError* error) {
   CHECK_EQ(GetCBPeripheral().state, CBPeripheralStateConnected);
   if (!characteristic_value_read_or_write_in_progress_) {
     // In case of buggy device, nothing should be done if receiving extra
     // write confirmation.
     VLOG(1) << "Write notification while no write operation pending.";
     return;
   }
@@ skipping 126 matching lines @@
               pair) {
         return pair.second->GetCBDescriptor() == cb_descriptor;
       });
   if (found == gatt_descriptor_macs_.end()) {
     return nullptr;
   } else {
     return found->second.get();
   }
 }
 }  // namespace device.