Update //third_party/protobuf to version 3.

third_party/protobuf/js/package.json

Index: third_party/protobuf/js/package.json
diff --git a/third_party/protobuf/js/package.json b/third_party/protobuf/js/package.json
new file mode 100644
index 0000000000000000000000000000000000000000..316be3169a6c6ea7f4328d39d55cf517676acdff
--- /dev/null
+++ b/third_party/protobuf/js/package.json
@@ -0,0 +1,21 @@
+{
+  "name": "google-protobuf",
+  "version": "3.0.0-alpha.5",
+  "description": "Protocol Buffers for JavaScript",
+  "main": "debug.js",
+  "dependencies": {
+    "google-closure-library": "~20151015.0.0",
+    "gulp": "~3.9.0",
+    "jasmine": "~2.4.1"
+  },
+  "devDependencies": {},
+  "scripts": {
+    "test": "./node_modules/gulp/bin/gulp.js test"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/google/protobuf/tree/master/js"
+  },
+  "author": "",
+  "license": "Apache-2.0"
+}