FDPT: Full Decrypt Path Testing Application

Cherry pick of http://go/ag/9326830

This is a merge of the full decrypt path testing CLs from the Widevine
repo: http://go/wvgerrit/q/topic:FDPT-subsamples

This is the Full Decrypt Path Testing application that can be used by
device makers to verify that OEMCrypto is correctly decrypting content
to secure buffers.

Testing: Ran App.
Bug: 113594822

Change-Id: Icbb1e2f2e762bac3cc1b7b20749922c14ea24449

libwvdrmengine/test/java/FullDecryptPathTesting/build.gradle

@@ -0,0 +1,27 @@
+// Top-level build file where you can add configuration options common to all sub-projects/modules.
+
+buildscript {
+    
+    repositories {
+        google()
+        jcenter()
+    }
+    dependencies {
+        classpath 'com.android.tools.build:gradle:3.2.1'
+        
+
+        // NOTE: Do not place your application dependencies here; they belong
+        // in the individual module build.gradle files
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        jcenter()
+    }
+}
+
+task clean(type: Delete) {
+    delete rootProject.buildDir
+}