Include the full certificate chain in the download pingback.

chrome/common/safe_browsing/csd.proto

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Client side phishing and malware detection request and response
 // protocol buffers.  Those protocol messages should be kept in sync
 // with the server implementation.
 //
 // If you want to change this protocol definition or you have questions
 // regarding its format please contact chrome-anti-phishing@googlegroups.com.
@@ skipping 106 matching lines @@
     optional string referrer = 4;
 
     // TODO(noelutz): add the transition type?
   }
 
   // This repeated field will store all the redirects as well as the
   // final URLs for the top-level tab URL (i.e., the URL that
   // triggered the download) as well as for the download URL itself.
   repeated Resource resources = 4;
 
+  // A trust chain of certificates.  Each chain begins with the signing
+  // certificate of the binary, and ends with a self-signed certificate,
+  // typically from a trusted root CA.  This structure is analogous to
+  // CERT_CHAIN_CONTEXT on Windows.
+  message CertificateChain {
+    // A single link in the chain.
+    message Element {
+      // DER-encoded X.509 representation of the certificate.
+      optional bytes certificate = 1;
+    }
+    repeated Element element = 1;
+  }
+
   message SignatureInfo {
-    // The full DER-encoded X.509 certificate extracted from the binary.
-    // If this field is not present, it means the binary was unsigned.
-    optional bytes certificate_contents = 1;
+    // All of the certificate chains for the binary's signing certificate.
+    // If no chains are present, the binary is not signed.  Multiple chains
+    // may be present if any certificate has multiple signers.
+    repeated CertificateChain certificate_chain = 1;
 
     // True if the signature was trusted on the client.
     optional bool trusted = 2;
   }
 
   // This field will only be set if the binary is signed.
   optional SignatureInfo signature = 5;
 
   // True if the download was user initiated.
   optional bool user_initiated = 6;
 }
 
 message ClientDownloadResponse {
   enum Verdict {
     // Download is considered safe.
     SAFE = 0;
     // Download is considered dangerous.  Chrome should show a warning to the
     // user.
     DANGEROUS = 1;
   }
   required Verdict verdict = 1;
 }