Replace hardcoded parameters

WORKSPACE

@@ -1,6 +1,6 @@
 workspace(name = "media_cas_packager_sdk")
-
 load("@bazel_tools//tools/build_defs/repo:git.bzl", "new_git_repository", "git_repository")
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 # CCTZ (Time-zone framework), needed by abseil.
 git_repository(
@@ -11,14 +11,33 @@ git_repository(
 
 git_repository(
     name = "abseil_repo",
-    commit = "475d64f2de7403a01b1b36c487328ed41d29c20c",  #2018-04-10
+    commit = "aa844899c937bde5d2b24f276b59997e5b668bde",  #2019-08-08
     remote = "https://github.com/abseil/abseil-cpp.git",
 )
 
+# Name com_google_protobuf instead of protobuf_repo because Bazel's proto rules
+# implicitly depend on @com_google_protobuf. See
+# https://bazel.build/blog/2017/02/27/protocol-buffers.html.
 git_repository(
-    name = "protobuf_repo",
+    name = "com_google_protobuf",
     remote = "https://github.com/google/protobuf.git",
-    tag = "v3.6.1.3",
+    tag = "v3.8.0",
+)
+
+# Bazel custom build rule support.
+git_repository(
+    name = "bazel_skylib",
+    remote = "https://github.com/bazelbuild/bazel-skylib.git",
+    tag = "0.8.0",
+)
+
+# Protobuf library support. Not included in the recent protobuf release.
+http_archive(
+    name = "zlib",
+    build_file = "@com_google_protobuf//:third_party/zlib.BUILD",
+    sha256 = "c3e5e9fdd5004dcb542feda5ee4f0ff0744628baf8ed2dd5d66f8ca1197cb1a1",
+    strip_prefix = "zlib-1.2.11",
+    urls = ["https://zlib.net/zlib-1.2.11.tar.gz"],
 )
 
 git_repository(
@@ -62,7 +81,7 @@ new_git_repository(
 
 bind(
     name = "protobuf",
-    actual = "@protobuf_repo//:protobuf",
+    actual = "@com_google_protobuf//:protobuf",
 )
 
 bind(