Add @Override annotation to MANAGER override template.

Example error set:
    (see http://errorprone.info/bugpattern/MissingOverride)
  Did you mean '@Override public AndroidOverlayProvider[] buildArray(int size) {'?
/tmp/tmpXyQKec/java/org/chromium/media/mojom/AudioDecoder_Internal.java:22: warning: [MissingOverride] getName implements method in Manager; expected @Override
        public String getName() {
                      ^
    (see http://errorprone.info/bugpattern/MissingOverride)
  Did you mean '@Override public String getName() {'?
/tmp/tmpXyQKec/java/org/chromium/media/mojom/AudioDecoder_Internal.java:26: warning: [MissingOverride] getVersion implements method in Manager; expected @Override
        public int getVersion() {
                   ^
    (see http://errorprone.info/bugpattern/MissingOverride)
  Did you mean '@Override public int getVersion() {'?
/tmp/tmpXyQKec/java/org/chromium/media/mojom/AudioDecoder_Internal.java:30: warning: [MissingOverride] buildProxy implements method in Manager; expected @Override
        public Proxy buildProxy(org.chromium.mojo.system.Core core,
                     ^
    (see http://errorprone.info/bugpattern/MissingOverride)
  Did you mean '@Override public Proxy buildProxy(org.chromium.mojo.system.Core core,'?
/tmp/tmpXyQKec/java/org/chromium/media/mojom/AudioDecoder_Internal.java:35: warning: [MissingOverride] buildStub implements method in Manager; expected @Override
        public Stub buildStub(org.chromium.mojo.system.Core core, AudioDecoder impl) {
                    ^
    (see http://errorprone.info/bugpattern/MissingOverride)
  Did you mean '@Override public Stub buildStub(org.chromium.mojo.system.Core core, AudioDecoder impl) {'?
/tmp/tmpXyQKec/java/org/chromium/media/mojom/AudioDecoder_Internal.java:39: warning: [MissingOverride] buildArray implements method in Manager; expected @Override
        public AudioDecoder[] buildArray(int size) {

BUG=

Change-Id: Ifab68faf81b4dbcf485cc8f624a7c857edf6c9fa
Reviewed-on: https://chromium-review.googlesource.com/820093Reviewed-by: Ken Rockot <rockot@chromium.org>
Commit-Queue: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523305}

mojo/public/tools/bindings/generators/java_templates/interface_definition.tmpl

@@ -58,23 +58,28 @@ org.chromium.mojo.bindings.MessageHeader.MESSAGE_IS_RESPONSE_FLAG
 public static final {{manager_class(interface, True)}} MANAGER =
         new {{manager_class(interface, True)}}() {
 
+    @Override
     public String getName() {
         return "{{namespace|replace(".","::")}}::{{interface.name}}";
     }
 
+    @Override
     public int getVersion() {
       return {{interface.version}};
     }
 
+    @Override
     public Proxy buildProxy(org.chromium.mojo.system.Core core,
                             org.chromium.mojo.bindings.MessageReceiverWithResponder messageReceiver) {
         return new Proxy(core, messageReceiver);
     }
 
+    @Override
     public Stub buildStub(org.chromium.mojo.system.Core core, {{interface|name}} impl) {
         return new Stub(core, impl);
     }
 
+    @Override
     public {{interface|name}}[] buildArray(int size) {
       return new {{interface|name}}[size];
     }