Define Buffer globally if buffer built-in module installed.

index.js

@@ -24,3 +24,18 @@ if (typeof meteorInstall === "function") {
     }
   });
 }
+
+// If Buffer is not defined globally, but the "buffer" built-in stub is
+// installed and can be imported, use it to define global.Buffer so that
+// modules like core-util-is/lib/util.js can refer to Buffer without
+// crashing application startup.
+if (typeof global.Buffer !== "function") {
+  try {
+    // Use (0, require)(...) to avoid registering a dependency on the
+    // "buffer" stub, in case it is not otherwise bundled.
+    global.Buffer = (0, require)("buffer");
+  } catch (ok) {
+    // Failure to import "buffer" is fine as long as the Buffer global
+    // variable is not used.
+  }
+}