Added support for ext4 ASEC resizing.

ASECs formatted as ext4 can now be resized using vdc asec resize.
Refactored some common code.
Requires resize2fs.

Change-Id: Ie78bb6015114a7bc4af42b16d1f299322ffc1e2a
Signed-off-by: Daniel Rosenberg <drosen@google.com>
diff --git a/VolumeManager.h b/VolumeManager.h
index cc8958d..07fd00e 100644
--- a/VolumeManager.h
+++ b/VolumeManager.h
@@ -91,6 +91,7 @@
             const char **directory = NULL) const;
     int createAsec(const char *id, unsigned numSectors, const char *fstype,
                    const char *key, const int ownerUid, bool isExternal);
+    int resizeAsec(const char *id, unsigned numSectors, const char *key);
     int finalizeAsec(const char *id);
 
     /**