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

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 6f364a95bdfc6691492d262f66216d746fd95b9d..4b994ce654a65e9188279eafc65adb50a61d3d9c 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -101,6 +101,8 @@ component("base") {
     "android/java_handler_thread.h",
     "android/java_runtime.cc",
     "android/java_runtime.h",
+    "android/java_system.cc",
+    "android/java_system.h",
     "android/jni_android.cc",
     "android/jni_android.h",
     "android/jni_array.cc",
@@ -1567,6 +1569,7 @@ if (is_android) {
 
     deps = [
       ":android_runtime_jni_headers",
+      ":android_system_jni_headers",
     ]
 
     jni_package = "base"
@@ -1578,6 +1581,12 @@ if (is_android) {
     classes = [ "java/lang/Runtime.class" ]
   }
 
+  # GYP: //base.gyp:android_system_jni_headers
+  generate_jar_jni("android_system_jni_headers") {
+    jni_package = "base"
+    classes = [ "java/lang/System.class" ]
+  }
+
   # GYP: //base.gyp:base_java
   android_library("base_java") {
     srcjar_deps = [