Upgrade to Bazel 0.19.0

Also replace native git_repository rule with Starlark rule. This is
needed because in recent Bazel versions native git_repository rule
is deprecated.

Change-Id: I2c19fd31693a930d7d35fdbb93bfa4abf21fa2aa
Signed-off-by: David Ostrovsky <david@ostrovsky.org>

WORKSPACE

@@ -11,7 +11,7 @@ http_archive(
 
 load("@bazel_skylib//:lib.bzl", "versions")
 
-versions.check(minimum_bazel_version = "0.17.1")
+versions.check(minimum_bazel_version = "0.19.0")
 
 load("//tools:bazlets.bzl", "load_bazlets")
 

tools/BUILD

@@ -6,7 +6,7 @@ load(
 
 default_java_toolchain(
     name = "error_prone_warnings_toolchain",
-    bootclasspath = ["@bazel_tools//tools/jdk:platformclasspath9.jar"],
+    bootclasspath = ["@bazel_tools//tools/jdk:platformclasspath.jar"],
     jvm_opts = JDK9_JVM_OPTS,
     package_configuration = [
         ":error_prone",

tools/bazlets.bzl

@@ -1,10 +1,12 @@
+load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
+
 NAME = "com_googlesource_gerrit_bazlets"
 
 def load_bazlets(
         commit,
         local_path = None):
     if not local_path:
-        native.git_repository(
+        git_repository(
             name = NAME,
             remote = "https://gerrit.googlesource.com/bazlets",
             commit = commit,