Improve jni_generator sample documentation.

base/android/jni_generator/sample_for_tests.cc

 // Copyright (c) 2012 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.
 
 #include "base/android/jni_generator/sample_for_tests.h"
 
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
-#include "jni/SampleForTests_jni.h"
-
+// Generated file for JNI bindings from C++ to Java @CalledByNative methods.
+// Only to be included in one .cc file.
+// Name is based on the java file name: *.java -> jni/*_jni.h
+#include "jni/SampleForTests_jni.h"  // Generated by JNI.
 
 using base::android::AttachCurrentThread;
 using base::android::ScopedJavaLocalRef;
 
 namespace base {
 namespace android {
 
 jdouble CPPClass::InnerClass::MethodOtherP0(JNIEnv* env, jobject obj) {
   return 0.0;
 }
 
 CPPClass::CPPClass() {
 }
 
 CPPClass::~CPPClass() {
 }
 
+// static
+bool CPPClass::RegisterJNI(JNIEnv* env) {
+  return RegisterNativesImpl(env);  // Generated in SampleForTests_jni.h
+}
+
 void CPPClass::Destroy(JNIEnv* env, jobject obj) {
   delete this;
 }
 
 jint CPPClass::Method(JNIEnv* env, jobject obj) {
   return 0;
 }
 
 void CPPClass::AddStructB(JNIEnv* env, jobject obj, jobject structb) {
   long key = Java_InnerStructB_getKey(env, structb);
@@ skipping 65 matching lines @@
     ScopedJavaLocalRef<jobject> struct_a =
         base::android::Java_InnerStructA_create(
             env, 0, 1,
             base::android::ConvertUTF8ToJavaString(env, "test").obj());
     base::android::Java_SampleForTests_addStructA(
         env, my_java_object, struct_a.obj());
   }
   base::android::Java_SampleForTests_iterateAndDoSomething(env, my_java_object);
   return 0;
 }