Android: Don't require RegisterNatives if there are none

base/android/jni_generator/testFromJavaPGenerics.golden

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file is autogenerated by
 //     base/android/jni_generator/jni_generator.py
 // For
 //     java/util/HashSet
 
 #ifndef java_util_HashSet_JNI
@@ skipping 15 matching lines @@
 }  // namespace
 
 namespace JNI_HashSet {
 
 // Step 2: method stubs.
 
 static base::subtle::AtomicWord g_HashSet_dummy = 0;
 static void Java_HashSet_dummy(JNIEnv* env, jobject obj) __attribute__
     ((unused));
 static void Java_HashSet_dummy(JNIEnv* env, jobject obj) {
-  /* Must call RegisterNativesImpl()  */
   CHECK_CLAZZ(env, obj,
       HashSet_clazz(env));
   jmethodID method_id =
       base::android::MethodID::LazyGet<
       base::android::MethodID::TYPE_INSTANCE>(
       env, HashSet_clazz(env),
       "dummy",
       "()V",
       &g_HashSet_dummy);
 
      env->CallVoidMethod(obj,
           method_id);
   jni_generator::CheckException(env);
 
 }
 
 // Step 3: RegisterNatives.
 
+static bool RegisterNativesImpl(JNIEnv* env) __attribute__((unused));
 static bool RegisterNativesImpl(JNIEnv* env) {
   if (base::android::IsManualJniRegistrationDisabled()) return true;
 
   return true;
 }
 
 }  // namespace JNI_HashSet
 
 #endif  // java_util_HashSet_JNI