Implement VerifyPayloadApplicable.

Parse the payload metadata and validate the source hash of all operations.
Return false if any error occur or hash mismatch.

Bug: 65283633
Test: mma

Change-Id: I6f5ae3cb69f4de973cecd0e3d7b733a48b2462f1
diff --git a/service_delegate_android_interface.h b/service_delegate_android_interface.h
index 7dae40f..5267bb0 100644
--- a/service_delegate_android_interface.h
+++ b/service_delegate_android_interface.h
@@ -70,6 +70,12 @@
   // of error, returns false and sets |error| accordingly.
   virtual bool ResetStatus(brillo::ErrorPtr* error) = 0;
 
+  // Verifies whether a payload (delegated by the payload metadata) can be
+  // applied to the current device. Returns whether the payload is applicable.
+  // In case of error, returns false and sets |error| accordingly.
+  virtual bool VerifyPayloadApplicable(const std::string& metadata_filename,
+                                       brillo::ErrorPtr* error) = 0;
+
  protected:
   ServiceDelegateAndroidInterface() = default;
 };