Extract the certificate to use in the download protection pingback.

chrome/browser/safe_browsing/download_protection_service.h

Index: chrome/browser/safe_browsing/download_protection_service.h
===================================================================
--- chrome/browser/safe_browsing/download_protection_service.h	(revision 108613)
+++ chrome/browser/safe_browsing/download_protection_service.h	(working copy)
@@ -28,6 +28,7 @@
 class SafeBrowsingService;
 
 namespace safe_browsing {
+class SignatureUtil;
 
 // This class provides an asynchronous API to check whether a particular
 // client download is malicious or not.
@@ -141,6 +142,9 @@
   // Keeps track of the state of the service.
   bool enabled_;
 
+  // SignatureUtil object, may be overridden for testing.
+  scoped_refptr<SignatureUtil> signature_util_;
+
   DISALLOW_COPY_AND_ASSIGN(DownloadProtectionService);
 };
 }  // namespace safe_browsing