Update the source sets configuration for the app and lib modules to match the default configuration

Both the `app` and `lib` modules had custom source sets configuration originating from the early days of the project. This updates the configuration to match the default Android Studio configuration which will simplify the addition of unit tests and instrumented tests to the project.

Note that for backcompat reasons, some folders (such as the `res` folder in the `app` module) are left as is.

platform/android/java/app/build.gradle

@@ -221,16 +221,10 @@ android {
     }
 
     sourceSets {
-        main {
-            manifest.srcFile 'AndroidManifest.xml'
-            java.srcDirs = ['src']
-            res.srcDirs = ['res']
-            aidl.srcDirs = ['aidl']
-            assets.srcDirs = ['assets']
-        }
-        debug.jniLibs.srcDirs = ['libs/debug', 'libs/debug/vulkan_validation_layers']
-        dev.jniLibs.srcDirs = ['libs/dev']
-        release.jniLibs.srcDirs = ['libs/release']
+        main.res.srcDirs += ['res']
+        debug.jniLibs.srcDirs += ['libs/debug', 'libs/debug/vulkan_validation_layers']
+        dev.jniLibs.srcDirs += ['libs/dev']
+        release.jniLibs.srcDirs += ['libs/release']
     }
 
     applicationVariants.all { variant ->

platform/android/java/lib/build.gradle

@@ -77,23 +77,14 @@ android {
     }
 
     sourceSets {
-        main {
-            manifest.srcFile 'AndroidManifest.xml'
-            java.srcDirs = ['src']
-            test.java.srcDirs = ['srcTest/java']
-            res.srcDirs = ['res']
-            aidl.srcDirs = ['aidl']
-            assets.srcDirs = ['assets']
-        }
-
-        debug.jniLibs.srcDirs = ['libs/debug']
-        dev.jniLibs.srcDirs = ['libs/dev']
-        release.jniLibs.srcDirs = ['libs/release']
+        debug.jniLibs.srcDirs += ['libs/debug']
+        dev.jniLibs.srcDirs += ['libs/dev']
+        release.jniLibs.srcDirs += ['libs/release']
 
         // Editor jni library
-        editorRelease.jniLibs.srcDirs = ['libs/tools/release']
-        editorDebug.jniLibs.srcDirs = ['libs/tools/debug']
-        editorDev.jniLibs.srcDirs = ['libs/tools/dev']
+        editorRelease.jniLibs.srcDirs += ['libs/tools/release']
+        editorDebug.jniLibs.srcDirs += ['libs/tools/debug']
+        editorDev.jniLibs.srcDirs += ['libs/tools/dev']
     }
 
     libraryVariants.all { variant ->

platform/android/java/lib/src/main/java/com/google/android/vending/expansion/downloader/impl/DownloadThread.java

@@ -110,7 +110,7 @@ public class DownloadThread {
      * headers, or destination filename.
      */
     private class StopRequest extends Throwable {
-    	
+
         private static final long serialVersionUID = 6338592678988347973L;
         public int mFinalStatus;
 

platform/android/java/lib/src/main/java/com/google/android/vending/licensing/LicenseChecker.java

@@ -133,7 +133,7 @@ public class LicenseChecker implements ServiceConnection {
      * <p>
      * source string: "com.android.vending.licensing.ILicensingService"
      * <p>
-     * 
+     *
      * @param callback
      */
     public synchronized void checkAccess(LicenseCheckerCallback callback) {