Pepper: Add IsAvailable() static methods to C++ wrappers to AudioInput_Dev and VideoCapture_Dev.

ppapi/cpp/dev/audio_input_dev.h

 // Copyright (c) 2011 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 PPAPI_CPP_DEV_AUDIO_INPUT_DEV_H_
 #define PPAPI_CPP_DEV_AUDIO_INPUT_DEV_H_
 
 #include "ppapi/c/dev/ppb_audio_input_dev.h"
 #include "ppapi/cpp/audio_config.h"
 #include "ppapi/cpp/resource.h"
 
 namespace pp {
 
 class Instance;
 
 class AudioInput_Dev : public Resource {
  public:
   /// An empty constructor for an AudioInput resource.
   AudioInput_Dev() {}
 
   AudioInput_Dev(Instance* instance,
                  const AudioConfig& config,
                  PPB_AudioInput_Callback callback,
                  void* user_data);
 
+  /// Static function for determining whether the browser supports the required
+  /// AudioInput interface.
+  ///
+  /// @return true if the interface is available, false otherwise.
+  static bool IsAvailable();
+
   /// Getter function for returning the internal <code>PPB_AudioConfig</code>
   /// struct.
   ///
   /// @return A mutable reference to the PPB_AudioConfig struct.
   AudioConfig& config() { return config_; }
 
   /// Getter function for returning the internal <code>PPB_AudioConfig</code>
   /// struct.
   ///
   /// @return A const reference to the internal <code>PPB_AudioConfig</code>
   /// struct.
   const AudioConfig& config() const { return config_; }
 
   bool StartCapture();
   bool StopCapture();
 
  private:
   AudioConfig config_;
 };
 
 }  // namespace pp
 
 #endif  // PPAPI_CPP_DEV_AUDIO_INPUT_DEV_H_