Add static MyMessage.parser().

In preparation of deprecating the PARSER public instance.

Change-Id: I3e332d83bc4b4f8467769f8e45c758978ace8f21

src/google/protobuf/compiler/java/java_message.cc

@@ -1250,6 +1250,10 @@ void ImmutableMessageGenerator::GenerateParser(io::Printer* printer) {
       "\n");
 
   printer->Print(
+      "public static com.google.protobuf.Parser<$classname$> parser() {\n"
+      "  return PARSER;\n"
+      "}\n"
+      "\n"
       "@java.lang.Override\n"
       "public com.google.protobuf.Parser<$classname$> getParserForType() {\n"
       "  return PARSER;\n"

src/google/protobuf/compiler/java/java_message_lite.cc

@@ -1153,7 +1153,10 @@ void ImmutableMessageLiteGenerator::GenerateParser(io::Printer* printer) {
   printer->Print(
       "public static final com.google.protobuf.Parser<$classname$> PARSER =\n"
       "    new DefaultInstanceBasedParser(DEFAULT_INSTANCE);\n"
-      "\n",
+      "\n"
+      "public static com.google.protobuf.Parser<$classname$> parser() {\n"
+      "  return PARSER;\n"
+      "}\n",
       "classname", descriptor_->name());
 }