[Nearby] Clarify misleading certificate storage logs

Notably, remove the log, "Overwriting private certificates pref with X
certificates." Some certificate might be overwritten but with no
material changes. For example, consumed salts--used to encrypt the
metadata key during advertising--need to be stored in the private
certificate. That update overwrites the certificate, but the certificate
remains essentially the same.

Change-Id: I99b120689d1371f844dac682c2e1c398d65b4c9b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2595191
Commit-Queue: Josh Nohle <nohle@chromium.org>
Commit-Queue: James Vecore <vecore@google.com>
Auto-Submit: Josh Nohle <nohle@chromium.org>
Reviewed-by: James Vecore <vecore@google.com>
Cr-Commit-Position: refs/heads/master@{#837836}

chrome/browser/nearby_sharing/certificates/nearby_share_certificate_storage.cc

@@ -4,8 +4,10 @@
 
 #include <algorithm>
 
+#include "base/strings/string_number_conversions.h"
 #include "chrome/browser/nearby_sharing/certificates/common.h"
 #include "chrome/browser/nearby_sharing/certificates/nearby_share_certificate_storage.h"
+#include "chrome/browser/nearby_sharing/logging/logging.h"
 
 base::Optional<base::Time>
 NearbyShareCertificateStorage::NextPrivateCertificateExpirationTime() {
@@ -25,17 +27,24 @@ void NearbyShareCertificateStorage::UpdatePrivateCertificate(
     const NearbySharePrivateCertificate& private_certificate) {
   base::Optional<std::vector<NearbySharePrivateCertificate>> certs =
       GetPrivateCertificates();
-  if (!certs)
+  if (!certs) {
+    NS_LOG(WARNING) << __func__ << ": No private certificates to update.";
     return;
+  }
 
   auto it = std::find_if(
       certs->begin(), certs->end(),
       [&private_certificate](const NearbySharePrivateCertificate& cert) {
         return cert.id() == private_certificate.id();
       });
-  if (it == certs->end())
+  if (it == certs->end()) {
+    NS_LOG(VERBOSE) << __func__ << ": No private certificate with id="
+                    << base::HexEncode(private_certificate.id());
     return;
+  }
 
+  NS_LOG(VERBOSE) << __func__ << ": Updating private certificate id="
+                  << base::HexEncode(private_certificate.id());
   *it = private_certificate;
   ReplacePrivateCertificates(*certs);
 }
@@ -56,10 +65,17 @@ void NearbyShareCertificateStorage::RemoveExpiredPrivateCertificates(
     }
   }
 
+  size_t num_removed = certs->size() - unexpired_certs.size();
+  if (num_removed == 0)
+    return;
+
+  NS_LOG(VERBOSE) << __func__ << ": Removing " << num_removed
+                  << " expired private certificates.";
   ReplacePrivateCertificates(unexpired_certs);
 }
 
 void NearbyShareCertificateStorage::ClearPrivateCertificates() {
+  NS_LOG(VERBOSE) << __func__ << ": Removing all private certificates.";
   ReplacePrivateCertificates(std::vector<NearbySharePrivateCertificate>());
 }
 
@@ -80,6 +96,10 @@ void NearbyShareCertificateStorage::ClearPrivateCertificatesOfVisibility(
     }
   }
 
-  if (were_certs_removed)
+  if (were_certs_removed) {
+    NS_LOG(VERBOSE) << __func__
+                    << ": Removing all private certificates of visibility "
+                    << visibility;
     ReplacePrivateCertificates(new_certs);
+  }
 }

chrome/browser/nearby_sharing/certificates/nearby_share_certificate_storage_impl.cc

@@ -330,7 +330,7 @@ void NearbyShareCertificateStorageImpl::
   }
 
   NS_LOG(VERBOSE) << __func__ << ": Inserting " << new_entries->size()
-                  << " new public certificates.";
+                  << " public certificates.";
   db_->UpdateEntries(
       std::move(new_entries),
       /*keys_to_remove=*/std::make_unique<std::vector<std::string>>(),
@@ -462,8 +462,6 @@ void NearbyShareCertificateStorageImpl::ReplacePrivateCertificates(
   for (const NearbySharePrivateCertificate& cert : private_certificates) {
     list.Append(cert.ToDictionary());
   }
-  NS_LOG(VERBOSE) << __func__ << ": Overwriting private certificates pref with "
-                  << private_certificates.size() << " certificates.";
   pref_service_->Set(prefs::kNearbySharingPrivateCertificateListPrefName, list);
 }
 
@@ -531,7 +529,7 @@ void NearbyShareCertificateStorageImpl::AddPublicCertificates(
   NS_LOG(VERBOSE)
       << __func__
       << ": Calling UpdateEntries on public certificate database with "
-      << public_certificates.size() << " new certificates.";
+      << public_certificates.size() << " certificates.";
   db_->UpdateEntries(
       std::move(new_entries), std::make_unique<std::vector<std::string>>(),
       base::BindOnce(