Reason for revert: Breaks downstream for SRTP include paths. Will rework this and reland without that one. Original issue's description: > Remove the rtc_relative_path GYP variable and similar defines > > The defines that can be used to alter the include paths for Expat, SRTP > and gtest are no longer needed in WebRTC or Chromium. Let's remove them > to simplify the GYP a little. > > Removed defines: > EXPAT_RELATIVE_PATH > GTEST_RELATIVE_PATH > SRTP_RELATIVE_PATH > > They're all set in the Chromium build so this shouldn't affect Chromium: > https://code.google.com/p/chromium/codesearch#chromium/src/third_party/libjingle/libjingle.gyp > > BUG=webrtc:4256 > NOTRY=True > NOPRESUBMIT=True > > Committed: https://crrev.com/e19cf59eb6ee44fd4d7e7fbcfdd1a6ea75063605 > Cr-Commit-Position: refs/heads/master@{#12467} TBR=pthatcher@webrtc.org,perkj@webrtc.org # Skipping CQ checks because original CL landed less than 1 days ago. NOPRESUBMIT=true NOTREECHECKS=true NOTRY=true BUG=webrtc:4256 Review URL: https://codereview.webrtc.org/1913043003 Cr-Commit-Position: refs/heads/master@{#12468}