Make verdict optional in csd proto.

chrome/browser/safe_browsing/download_protection_service_unittest.cc

Index: chrome/browser/safe_browsing/download_protection_service_unittest.cc
diff --git a/chrome/browser/safe_browsing/download_protection_service_unittest.cc b/chrome/browser/safe_browsing/download_protection_service_unittest.cc
index 22c9bae31b25eb536a8b6d62f18570ebee0c3996..06d100c3d46ceaaa272f7240aab759daa4ba9ef7 100644
--- a/chrome/browser/safe_browsing/download_protection_service_unittest.cc
+++ b/chrome/browser/safe_browsing/download_protection_service_unittest.cc
@@ -1079,7 +1079,7 @@ TEST_F(DownloadProtectionServiceTest, CheckClientDownloadSuccess) {
     ClearClientDownloadRequest();
   }
   {
-    // Invalid response should result in UNKNOWN.
+    // Invalid response should result in SAFE (default value in proto).
     ClientDownloadResponse invalid_response;
     factory.SetFakeResponse(DownloadProtectionService::GetDownloadRequestUrl(),
                             invalid_response.SerializePartialAsString(),
@@ -1089,7 +1089,7 @@ TEST_F(DownloadProtectionServiceTest, CheckClientDownloadSuccess) {
         &item, base::Bind(&DownloadProtectionServiceTest::CheckDoneCallback,
                           base::Unretained(this), run_loop.QuitClosure()));
     run_loop.Run();
-    EXPECT_TRUE(IsResult(DownloadProtectionService::UNKNOWN));
+    EXPECT_TRUE(IsResult(DownloadProtectionService::SAFE));
     EXPECT_TRUE(HasClientDownloadRequest());
     ClearClientDownloadRequest();
     EXPECT_FALSE(DownloadFeedbackService::GetPingsForDownloadForTesting(