Revert of Remove the rtc_relative_path GYP variable and similar defines

webrtc/pc/externalhmac.h

 /*
  *  Copyright 2014 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 13 matching lines @@
 // can plug any desired authentication modules into libsrtp.
 // libsrtp also provides a mechanism to select different auth functions for
 // individual streams. This can be done by setting the right value in
 // the auth_type of srtp_policy_t. The application must first register auth
 // functions and the corresponding authentication id using
 // crypto_kernel_replace_auth_type function.
 #if defined(HAVE_SRTP) && defined(ENABLE_EXTERNAL_AUTH)
 
 #include "webrtc/base/basictypes.h"
 extern "C" {
+#ifdef SRTP_RELATIVE_PATH
+#include "auth.h"  // NOLINT
+#else
 #include "third_party/libsrtp/srtp/crypto/include/auth.h"
+#endif  // SRTP_RELATIVE_PATH
 }
 
 #define EXTERNAL_HMAC_SHA1 HMAC_SHA1 + 1
 #define HMAC_KEY_LENGTH 20
 
 // The HMAC context structure used to store authentication keys.
 // The pointer to the key  will be allocated in the external_hmac_init function.
 // This pointer is owned by srtp_t in a template context.
 typedef struct {
   uint8_t key[HMAC_KEY_LENGTH];
@@ skipping 17 matching lines @@
 err_status_t external_hmac_compute(ExternalHmacContext* state,
                                    const void* message,
                                    int msg_octets,
                                    int tag_len,
                                    uint8_t* result);
 
 err_status_t external_crypto_init();
 
 #endif  // defined(HAVE_SRTP) && defined(ENABLE_EXTERNAL_AUTH)
 #endif  // TALK_SESSION_MEDIA_EXTERNAL_HMAC_H_