Fix lint error/warning while building android template

platform/android/java/README.md

@@ -0,0 +1,47 @@
+# Third party libraries
+
+
+## Google's vending library
+
+- Upstream: https://github.com/google/play-licensing/tree/master/lvl_library/src/main/java/com/google/android/vending
+- Version: git (eb57657, 2018) with modifications
+- License: Apache 2.0
+
+Overwrite all files under `com/google/android/vending`
+
+### Modify some files to avoid compile error and lint warning
+
+#### com/google/android/vending/licensing/util/Base64.java
+```
+@@ -338,7 +338,8 @@ public class Base64 {
+                        e += 4;
+                }
+ 
+-               assert (e == outBuff.length);
++               if (BuildConfig.DEBUG && e != outBuff.length)
++                       throw new RuntimeException();
+                return outBuff;
+        }
+```
+
+#### com/google/android/vending/licensing/LicenseChecker.java
+```
+@@ -29,8 +29,8 @@ import android.os.RemoteException;
+ import android.provider.Settings.Secure;
+ import android.util.Log;
+ 
+-import com.android.vending.licensing.ILicenseResultListener;
+-import com.android.vending.licensing.ILicensingService;
++import com.google.android.vending.licensing.ILicenseResultListener;
++import com.google.android.vending.licensing.ILicensingService;
+ import com.google.android.vending.licensing.util.Base64;
+ import com.google.android.vending.licensing.util.Base64DecoderException;
+```
+```
+@@ -287,13 +287,15 @@ public class LicenseChecker implements ServiceConnection {
+     if (logResponse) {
+-        String android_id = Secure.getString(mContext.getContentResolver(),
+-                            Secure.ANDROID_ID);
++        String android_id = Secure.ANDROID_ID;
+         Date date = new Date();
+```