Removing EXPAT_RELATIVE_PATH and rtc_relative_path.

I think this was previously used in libjingle but it is not
used in WebRTC.

BUG=webrtc:8082

Review-Url: https://codereview.webrtc.org/2999703002
Cr-Original-Commit-Position: refs/heads/master@{#19523}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: cb2bbce4e1920c874c76dcfcc54d6c9922c4ea4d
diff --git a/BUILD.gn b/BUILD.gn
index f8ffd49..b5c832d 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -43,7 +43,6 @@
       # TODO(kjellander): Cleanup unused ones and move defines closer to
       # the source when webrtc:4256 is completed.
       "FEATURE_ENABLE_VOICEMAIL",
-      "EXPAT_RELATIVE_PATH",
       "GTEST_RELATIVE_PATH",
       "WEBRTC_CHROMIUM_BUILD",
     ]
@@ -125,10 +124,6 @@
     defines += [ "WEBRTC_INCLUDE_INTERNAL_AUDIO_DEVICE" ]
   }
 
-  if (rtc_relative_path) {
-    defines += [ "EXPAT_RELATIVE_PATH" ]
-  }
-
   if (!rtc_libvpx_build_vp9) {
     defines += [ "RTC_DISABLE_VP9" ]
   }
diff --git a/webrtc.gni b/webrtc.gni
index 72e031e..af4d6f9 100644
--- a/webrtc.gni
+++ b/webrtc.gni
@@ -43,9 +43,6 @@
   # Enable this to let the Opus audio codec change complexity on the fly.
   rtc_opus_variable_complexity = false
 
-  # Disable to use absolute header paths for some libraries.
-  rtc_relative_path = true
-
   # Used to specify an external Jsoncpp include path when not compiling the
   # library that comes with WebRTC (i.e. rtc_build_json == 0).
   rtc_jsoncpp_root = "//third_party/jsoncpp/source/include"