AU: Split applied update verification into a separate step.

Use instances of FilesystemCopierAction to do applied update verification. This
speeds it up slightly because asynchronous reads happen in parallel with hash
calculation but, more importantly, makes update_engine be responsive to D-Bus
during that step.

BUG=9140
TEST=unit tests, tested on device

Change-Id: I3ec9445de5e8258a63433a61f1a476aef4434f6c

Review URL: http://codereview.chromium.org/5516009
diff --git a/generate_delta_main.cc b/generate_delta_main.cc
index 39a0e08..6e9e553 100644
--- a/generate_delta_main.cc
+++ b/generate_delta_main.cc
@@ -90,8 +90,8 @@
     vector<char> root_hash(root_info.hash().begin(),
                            root_info.hash().end());
     DeltaPerformer performer(&prefs);
-    performer.set_current_kernel_hash(&kern_hash);
-    performer.set_current_rootfs_hash(&root_hash);
+    performer.set_current_kernel_hash(kern_hash);
+    performer.set_current_rootfs_hash(root_hash);
     CHECK_EQ(performer.Open(FLAGS_old_image.c_str(), 0, 0), 0);
     CHECK(performer.OpenKernel(FLAGS_old_kernel.c_str()));
     vector<char> buf(1024 * 1024);