Revert of Remove some warning suppressions from SocketRocket. (patchset #1 id:1 of https://codereview.webrtc.org/2704383004/ )

Reason for revert:
Breaks buildbot

Original issue's description:
> Remove some warning suppressions from SocketRocket.
>
> These warnings started appearing on a clang update. This CL patches the
> vendored library and removes the supression. We assert on the return as
> we're not equipped to deal with failures there anyway.
>
> BUG=webrtc:6396
> NOTRY=true
>
> Review-Url: https://codereview.webrtc.org/2704383004
> Cr-Commit-Position: refs/heads/master@{#16820}
> Committed: https://chromium.googlesource.com/external/webrtc/+/49990e88fb523901b28d10f2026602cb86528b0d

TBR=kjellander@webrtc.org,magjed@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6396

Review-Url: https://codereview.webrtc.org/2714123002
Cr-Commit-Position: refs/heads/master@{#16822}
diff --git a/webrtc/examples/BUILD.gn b/webrtc/examples/BUILD.gn
index d0808b1..0098d69 100644
--- a/webrtc/examples/BUILD.gn
+++ b/webrtc/examples/BUILD.gn
@@ -393,11 +393,16 @@
       "-Wno-deprecated-declarations",
       "-Wno-nonnull",
       "-Wno-semicolon-before-method-body",
+      "-Wno-unused-variable",
     ]
 
     cflags_objc = [
       # Enabled for cflags_objc in build/config/compiler/BUILD.gn.
       "-Wno-objc-missing-property-synthesis",
+
+      # Hide the warning for SecRandomCopyBytes(), until we update to upstream.
+      # https://bugs.chromium.org/p/webrtc/issues/detail?id=6396
+      "-Wno-unused-result",
     ]
   }