Update protobuf version to 3.7.0

BUILD

@@ -0,0 +1 @@
+# Empty Bazel build file

WORKSPACE

@@ -1,10 +1,26 @@
 workspace(name = "io_bazel_rules_closure")
 
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 load("//closure/private:java_import_external.bzl", "java_import_external")
 load("//closure:repositories.bzl", "closure_repositories")
 
 closure_repositories()
 
+http_archive(
+    name = "net_zlib",
+    build_file = "//:third_party/zlib.BUILD",
+    sha256 = "c3e5e9fdd5004dcb542feda5ee4f0ff0744628baf8ed2dd5d66f8ca1197cb1a1",
+    strip_prefix = "zlib-1.2.11",
+    urls = ["https://zlib.net/zlib-1.2.11.tar.gz"],
+)
+
+http_archive(
+    name = "bazel_skylib",
+    sha256 = "bbccf674aa441c266df9894182d80de104cabd19be98be002f6d478aaa31574d",
+    strip_prefix = "bazel-skylib-2169ae1c374aab4a09aa90e65efe1a3aad4e279b",
+    urls = ["https://github.com/bazelbuild/bazel-skylib/archive/2169ae1c374aab4a09aa90e65efe1a3aad4e279b.tar.gz"],
+)
+
 java_import_external(
     name = "com_google_guava_testlib",
     jar_sha256 = "1e7e0e728bb8d68a985115d2439ad6a36473c3e49d78a70945919731f9ac7136",
@@ -82,3 +98,8 @@ java_import_external(
     testonly_ = 1,
     deps = ["@com_google_guava"],
 )
+
+bind(
+    name = "zlib",
+    actual = "@net_zlib//:zlib",
+)

third_party/zlib.BUILD

@@ -0,0 +1,60 @@
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # BSD/MIT-like license (for zlib)
+
+_ZLIB_HEADERS = [
+    "crc32.h",
+    "deflate.h",
+    "gzguts.h",
+    "inffast.h",
+    "inffixed.h",
+    "inflate.h",
+    "inftrees.h",
+    "trees.h",
+    "zconf.h",
+    "zlib.h",
+    "zutil.h",
+]
+
+_ZLIB_PREFIXED_HEADERS = ["zlib/include/" + hdr for hdr in _ZLIB_HEADERS]
+
+# In order to limit the damage from the `includes` propagation
+# via `:zlib`, copy the public headers to a subdirectory and
+# expose those.
+genrule(
+    name = "copy_public_headers",
+    srcs = _ZLIB_HEADERS,
+    outs = _ZLIB_PREFIXED_HEADERS,
+    cmd = "cp $(SRCS) $(@D)/zlib/include/",
+    visibility = ["//visibility:private"],
+)
+
+cc_library(
+    name = "zlib",
+    srcs = [
+        "adler32.c",
+        "compress.c",
+        "crc32.c",
+        "deflate.c",
+        "gzclose.c",
+        "gzlib.c",
+        "gzread.c",
+        "gzwrite.c",
+        "infback.c",
+        "inffast.c",
+        "inflate.c",
+        "inftrees.c",
+        "trees.c",
+        "uncompr.c",
+        "zutil.c",
+        # Include the un-prefixed headers in srcs to work
+        # around the fact that zlib isn't consistent in its
+        # choice of <> or "" delimiter when including itself.
+    ] + _ZLIB_HEADERS,
+    hdrs = _ZLIB_PREFIXED_HEADERS,
+    copts = [
+        "-Wno-unused-variable",
+        "-Wno-implicit-function-declaration",
+    ],
+    includes = ["zlib/include/"],
+)