base: Fix/add header #ifndef guards.

base/android/jni_generator/sample_for_tests.h

Index: base/android/jni_generator/sample_for_tests.h
diff --git a/base/android/jni_generator/sample_for_tests.h b/base/android/jni_generator/sample_for_tests.h
index 4d76408b686b64b0d2dc61e85a0931e0a37d7983..c98cf97693638963a322c3fd582bb7f541f526b1 100644
--- a/base/android/jni_generator/sample_for_tests.h
+++ b/base/android/jni_generator/sample_for_tests.h
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#ifndef BASE_ANDROID_JNI_GENERATOR_SAMPLE_FOR_TESTS_H_
+#define BASE_ANDROID_JNI_GENERATOR_SAMPLE_FOR_TESTS_H_
+
 #include <jni.h>
 #include <map>
 #include <string>
@@ -48,3 +51,5 @@ class CPPClass {
 
 }  // namespace android
 }  // namespace base
+
+#endif  // BASE_ANDROID_JNI_GENERATOR_SAMPLE_FOR_TESTS_H_