[CrOS Tether] Add a static TruncateDeviceIdForLogs() function.

BUG=672263

Review-Url: https://codereview.chromium.org/2590713002
Cr-Commit-Position: refs/heads/master@{#439730}

components/cryptauth/remote_device.cc

@@ -36,12 +36,7 @@ std::string RemoteDevice::GetDeviceId() const {
 }
 
 std::string RemoteDevice::GetTruncatedDeviceIdForLogs() const {
-   std::string id = GetDeviceId();
-   if (id.length() <= 10) {
-      return id;
-   }
-
-   return id.substr(0, 5) + "..." + id.substr(id.length() - 5, id.length());
+  return RemoteDevice::TruncateDeviceIdForLogs(GetDeviceId());
 }
 
 bool RemoteDevice::operator==(const RemoteDevice& other) const {
@@ -54,4 +49,15 @@ bool RemoteDevice::operator==(const RemoteDevice& other) const {
       && sign_in_challenge == other.sign_in_challenge;
 }
 
+// static
+std::string RemoteDevice::TruncateDeviceIdForLogs(const std::string& full_id) {
+  if (full_id.length() <= 10) {
+    return full_id;
+  }
+
+  return full_id.substr(0, 5)
+      + "..."
+      + full_id.substr(full_id.length() - 5, full_id.length());
+}
+
 }  // namespace cryptauth

components/cryptauth/remote_device.h

@@ -42,6 +42,9 @@ struct RemoteDevice {
   std::string GetTruncatedDeviceIdForLogs() const;
 
   bool operator==(const RemoteDevice& other) const;
+
+  // Static method for truncated device ID for logs.
+  static std::string TruncateDeviceIdForLogs(const std::string& full_id);
 };
 
 typedef std::vector<RemoteDevice> RemoteDeviceList;