Android: Use linker script to hide all non-JNI symbols

build/android/android_only_explicit_jni_exports.lst

Index: build/android/android_only_explicit_jni_exports.lst
diff --git a/build/android/android_only_explicit_jni_exports.lst b/build/android/android_only_explicit_jni_exports.lst
new file mode 100644
index 0000000000000000000000000000000000000000..f989691865b267b4a3c47a64459ad01c63bba037
--- /dev/null
+++ b/build/android/android_only_explicit_jni_exports.lst
@@ -0,0 +1,13 @@
+# Copyright 2017 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.
+
+# Linker script that exports only JNI_OnLoad.
+# Should be used for libraries that do explicit JNI registration.
+
+{
+  global:
+    JNI_OnLoad;
+  local:
+    *;
+};