Remove ComputeSourceHash mode in FileSystemVerification action.

This mode was used to calculate the source partition hash before download
the payload, and we will verify it against the hash in the payload.
Now that we are using per-operation source hash, this mode is no longer
needed.

Test: ./update_engine_unittests
Test: cros_workon_make update_engine --test
Bug: 26972259

Change-Id: Ie30a38cfd9f94e4efe02dfc8664e6785018261f6
diff --git a/update_attempter_android.cc b/update_attempter_android.cc
index e42f569..9f46536 100644
--- a/update_attempter_android.cc
+++ b/update_attempter_android.cc
@@ -399,9 +399,8 @@
       hardware_,
       nullptr,                                        // system_state, not used.
       new MultiRangeHttpFetcher(download_fetcher)));  // passes ownership
-  shared_ptr<FilesystemVerifierAction> dst_filesystem_verifier_action(
-      new FilesystemVerifierAction(boot_control_,
-                                   VerifierMode::kVerifyTargetHash));
+  shared_ptr<FilesystemVerifierAction> filesystem_verifier_action(
+      new FilesystemVerifierAction(boot_control_));
 
   shared_ptr<PostinstallRunnerAction> postinstall_runner_action(
       new PostinstallRunnerAction(boot_control_));
@@ -411,15 +410,14 @@
 
   actions_.push_back(shared_ptr<AbstractAction>(install_plan_action));
   actions_.push_back(shared_ptr<AbstractAction>(download_action));
-  actions_.push_back(
-      shared_ptr<AbstractAction>(dst_filesystem_verifier_action));
+  actions_.push_back(shared_ptr<AbstractAction>(filesystem_verifier_action));
   actions_.push_back(shared_ptr<AbstractAction>(postinstall_runner_action));
 
   // Bond them together. We have to use the leaf-types when calling
   // BondActions().
   BondActions(install_plan_action.get(), download_action.get());
-  BondActions(download_action.get(), dst_filesystem_verifier_action.get());
-  BondActions(dst_filesystem_verifier_action.get(),
+  BondActions(download_action.get(), filesystem_verifier_action.get());
+  BondActions(filesystem_verifier_action.get(),
               postinstall_runner_action.get());
 
   // Enqueue the actions.