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

chrome/test/BUILD.gn

Index: chrome/test/BUILD.gn
diff --git a/chrome/test/BUILD.gn b/chrome/test/BUILD.gn
index 95df486d1a720990e5462924b819003efefc3f3b..ec9a91ba96d0bf183fd8fdbba26fc3eab7e58953 100644
--- a/chrome/test/BUILD.gn
+++ b/chrome/test/BUILD.gn
@@ -2012,9 +2012,14 @@ source_set("test_support_unit") {
     "//chrome/browser",
     "//chrome/common",
     "//mojo/environment:chromium",
-    "//third_party/mojo/src/mojo/edk/system",
   ]
 
+  if (use_chrome_edk) {
+    deps += [ "//mojo/edk/system" ]
+  } else {
+    deps += [ "//third_party/mojo/src/mojo/edk/system" ]
+  }
+
   if (!is_android && use_ash) {
     sources += rebase_path(
             chrome_tests_unit_gypi_values.chrome_test_support_unit_ash_sources,