headless: Don't delete log files in child processes

headless/lib/headless_content_main_delegate.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 "headless/lib/headless_content_main_delegate.h"
 
 #include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/path_service.h"
 #include "base/run_loop.h"
@@ skipping 95 matching lines @@
 
   base::FilePath log_path;
   logging::LoggingSettings settings;
 
   if (PathService::Get(base::DIR_MODULE, &log_path)) {
     log_path = log_path.Append(log_filename);
   } else {
     log_path = log_filename;
   }
 
+  const std::string process_type =
+      command_line.GetSwitchValueASCII(switches::kProcessType);
+
   settings.logging_dest = log_mode;
   settings.log_file = log_path.value().c_str();
   settings.lock_log = logging::DONT_LOCK_LOG_FILE;
-  settings.delete_old = logging::DELETE_OLD_LOG_FILE;
+  settings.delete_old = process_type.empty() ? logging::DELETE_OLD_LOG_FILE
+                                             : logging::APPEND_TO_OLD_LOG_FILE;
   bool success = logging::InitLogging(settings);
   DCHECK(success);
 }
 
 void HeadlessContentMainDelegate::PreSandboxStartup() {
   InitLogging(*base::CommandLine::ForCurrentProcess());
   InitializeResourceBundle();
 }
 
 int HeadlessContentMainDelegate::RunProcess(
@@ skipping 53 matching lines @@
       pak_file, ui::SCALE_FACTOR_NONE);
 }
 
 content::ContentBrowserClient*
 HeadlessContentMainDelegate::CreateContentBrowserClient() {
   browser_client_.reset(new HeadlessContentBrowserClient(browser_.get()));
   return browser_client_.get();
 }
 
 }  // namespace headless