chrome.bluetoothLowEnergy: Implement readDescriptorValue.

chrome/browser/extensions/api/bluetooth_low_energy/bluetooth_low_energy_api.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 CHROME_BROWSER_EXTENSIONS_API_BLUETOOTH_LOW_ENERGY_BLUETOOTH_LOW_ENERGY_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_BLUETOOTH_LOW_ENERGY_BLUETOOTH_LOW_ENERGY_API_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "extensions/browser/browser_context_keyed_api_factory.h"
 #include "extensions/browser/extension_function.h"
@@ skipping 201 matching lines @@
     : public BluetoothLowEnergyExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("bluetoothLowEnergy.readDescriptorValue",
                              BLUETOOTHLOWENERGY_READDESCRIPTORVALUE);
 
  protected:
   virtual ~BluetoothLowEnergyReadDescriptorValueFunction() {}
 
   // BluetoothLowEnergyExtensionFunction override.
   virtual bool DoWork() OVERRIDE;
+
+ private:
+  // Success and error callbacks, called by
+  // BluetoothLowEnergyEventRouter::ReadDescriptorValue.
+  void SuccessCallback();
+  void ErrorCallback();
+
+  // The instance ID of the requested descriptor.
+  std::string instance_id_;
 };
 
 class BluetoothLowEnergyWriteDescriptorValueFunction
     : public BluetoothLowEnergyExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("bluetoothLowEnergy.writeDescriptorValue",
                              BLUETOOTHLOWENERGY_WRITEDESCRIPTORVALUE);
 
  protected:
   virtual ~BluetoothLowEnergyWriteDescriptorValueFunction() {}
 
   // BluetoothLowEnergyExtensionFunction override.
   virtual bool DoWork() OVERRIDE;
 };
 
 }  // namespace api
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_BLUETOOTH_LOW_ENERGY_BLUETOOTH_LOW_ENERGY_API_H_