Add a Mojo EDK for Chrome that uses one OS pipe per message pipe.

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 488768d84f71fba10b8f55f9531f0827e5ba9c00..d2d8256a49cb69a1f81d4ae7c98844907a70600e 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -289,6 +289,9 @@ config("feature_flags") {
   if (!fieldtrial_testing_like_official_build && !is_chrome_branded) {
     defines += [ "FIELDTRIAL_TESTING_ENABLED" ]
   }
+  if (use_chrome_edk) {
+    defines += [ "USE_CHROME_EDK" ]
+  }
 }
 
 # Debug/release ----------------------------------------------------------------