Simplify LogImpl a bit.

services/log/log_impl.cc

 // Copyright 2015 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.
 
 #include "services/log/log_impl.h"
 
-#include <stdio.h>
-
 #include <utility>
 
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "mojo/public/cpp/application/application_connection.h"
 #include "mojo/services/log/interfaces/entry.mojom.h"
 
 namespace mojo {
 namespace log {
 namespace {
@@ skipping 15 matching lines @@
     case kLogLevelError:
       return "ERROR";
   }
   return "FATAL";
 }
 
 }  // namespace
 
 LogImpl::LogImpl(const std::string& remote_url,
                  InterfaceRequest<Log> request,
-                 FILE* out_file)
+                 PrintLogMessageFunction print_log_message_function)
     : remote_url_(remote_url),
       binding_(this, std::move(request)),
-      out_file_(out_file) {}
+      print_log_message_function_(print_log_message_function) {}
 
 LogImpl::~LogImpl() {}
 
 // static
 void LogImpl::Create(ApplicationConnection* connection,
                      InterfaceRequest<Log> request,
-                     FILE* out_file) {
+                     PrintLogMessageFunction print_log_message_function) {
   DCHECK(connection);
-  DCHECK(out_file);
+  DCHECK(print_log_message_function);
 
   const std::string& remote_url = connection->GetRemoteApplicationURL();
   if (remote_url.empty()) {
     LOG(ERROR) << "No remote URL.";
     return;
   }
 
-  new LogImpl(remote_url, std::move(request), out_file);
+  new LogImpl(remote_url, std::move(request),
+              std::move(print_log_message_function));
 }
 
 void LogImpl::AddEntry(EntryPtr entry) {
   DCHECK(entry);
-
-  // In order to keep LogImpl thread-safe (for the future), we should only print
-  // one thing here (otherwise, it could interleave with other prints).
-  fprintf(out_file_, "%s\n", FormatEntry(entry).c_str());
+  print_log_message_function_(FormatEntry(entry));
 }
 
 // This should return:
 // <REMOTE_URL> [LOG_LEVEL] SOURCE_FILE:SOURCE_LINE MESSAGE
 std::string LogImpl::FormatEntry(const EntryPtr& entry) {
   std::string source;
   if (entry->source_file) {
     source += entry->source_file.To<std::string>();
     if (entry->source_line) {
       base::StringAppendF(&source, ":%u", entry->source_line);
     }
     source += ": ";
   }
 
   return base::StringPrintf(
       "<%s> [%s] %s%s", remote_url_.c_str(),
       LogLevelToString(entry->log_level).c_str(), source.c_str(),
       entry->message ? entry->message.To<std::string>().c_str()
                      : "<no message>");
 }
 
 }  // namespace log
 }  // namespace mojo