Unveil Bazel's proto_library and java_proto_library.

--
MOS_MIGRATED_REVID=127543896

src/main/java/com/google/devtools/build/lib/bazel/rules/java/proto/BazelJavaProtoLibraryRule.java

@@ -38,8 +38,6 @@ public BazelJavaProtoLibraryRule(BazelJavaProtoAspect javaProtoAspect) {
   @Override
   public RuleClass build(RuleClass.Builder builder, RuleDefinitionEnvironment environment) {
     return builder
-        // This rule isn't ready for use yet.
-        .setUndocumented()
         /* <!-- #BLAZE_RULE(java_proto_library).ATTRIBUTE(deps) -->
         The list of <a href="protocol-buffer.html#proto_library"><code>proto_library</code></a>
         rules to generate Java code for.

src/main/java/com/google/devtools/build/lib/rules/proto/BazelProtoLibraryRule.java

@@ -51,10 +51,6 @@ public RuleClass build(Builder builder, final RuleDefinitionEnvironment env) {
 
     return builder
         .requiresConfigurationFragments(ProtoConfiguration.class)
-        // This rule works, but does nothing, in open-source Bazel, due to the
-        // lack of protoc support. Users can theoretically write their own Skylark rules,
-        // but these are still 'experimental' according to the documentation.
-        .setUndocumented()
         .setOutputToGenfiles()
         .add(
             attr(":proto_compiler", LABEL)
@@ -97,7 +93,8 @@ public Metadata getMetadata() {
 
 <p>Use <code>proto_library</code> to define libraries of protocol buffers
    which may be used from multiple languages. A <code>proto_library</code> may be listed
-   in the <code>deps</code> clause of supported rules, such as <code>objc_proto_library</code>.
+   in the <code>deps</code> clause of supported rules, such as <code>java_proto_library</code> and
+   <code>objc_proto_library</code>.
 </p>
 
 <!-- #END_BLAZE_RULE -->*/