[Android] Add a java.lang.System wrapper.

base/android/java_system.cc

+// Copyright (c) 2015 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/java_system.h"
+
+#include "base/android/jni_string.h"
+#include "jni/System_jni.h"
+
+namespace base {
+namespace android {
+
+bool JavaSystem::Register(JNIEnv* env) {
+  return JNI_System::RegisterNativesImpl(env);
+}
+
+// static
+std::string JavaSystem::GetProperty(const base::StringPiece& property_name) {
+  DCHECK(!property_name.empty());
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jstring> jproperty_name =
+      ConvertUTF8ToJavaString(env, property_name);
+  ScopedJavaLocalRef<jstring> jproperty =
+      JNI_System::Java_System_getPropertyJLS_JLS(env, jproperty_name.obj());
+  return jproperty.is_null() ? std::string()
+                             : ConvertJavaStringToUTF8(env, jproperty.obj());
+}
+
+}  // namespace android
+}  // namespace base