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

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index 4a558d8db5cfc597f3733ffc3f989e629619c276..f5d0fbd49a18343c92991ef55711181861a7d873 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -1381,6 +1381,7 @@
           },
           'dependencies': [
             'android_runtime_jni_headers',
+            'android_system_jni_headers',
           ],
           'includes': [ '../build/jni_generator.gypi' ],
         },
@@ -1395,6 +1396,16 @@
           'includes': [ '../build/jar_file_jni_generator.gypi' ],
         },
         {
+          # GN: //base:android_system_jni_headers
+          'target_name': 'android_system_jni_headers',
+          'type': 'none',
+          'variables': {
+             'jni_gen_package': 'base',
+             'input_java_class': 'java/lang/System.class',
+           },
+          'includes': [ '../build/jar_file_jni_generator.gypi' ],
+        },
+        {
           # TODO(GN)
           'target_name': 'base_unittests_jni_headers',
           'type': 'none',