Invoke BLKSECDISCARD to securely delete sensitive data

Bug: 34600579
Test: manual - change device lock under synthetic password, verify
      old data on disk is erased.

Change-Id: I247bd1f095dd27335e671981f9e2d77e149af84f

core/java/android/os/storage/IStorageManager.aidl

@@ -295,4 +295,5 @@ interface IStorageManager {
     long getCacheSizeBytes(String volumeUuid, int uid) = 76;
     long getAllocatableBytes(String volumeUuid, int flags) = 77;
     void allocateBytes(String volumeUuid, long bytes, int flags) = 78;
+    void secdiscard(in String path) = 79;
 }

core/java/android/os/storage/StorageManager.java

@@ -1251,6 +1251,15 @@ public class StorageManager {
         }
     }
 
+    /** {@hide} */
+    public void secdiscard(String path) {
+        try {
+            mStorageManager.secdiscard(path);
+        } catch (RemoteException e) {
+            throw e.rethrowFromSystemServer();
+        }
+    }
+
     /** {@hide} */
     public static boolean isUserKeyUnlocked(int userId) {
         if (sStorageManager == null) {