debugd: Fix coding style and cpplint issues.

BUG=chromium:385849
TEST=`FEATURES=test emerge-$BOARD platform2`
TEST=`cpplint.py --root=src --filter=-build/include src/{*.h,*.cc,*/*.cc}`

Change-Id: Ia2475d6ee287dc727c3b2ffe139e9cc8bfe2e2e5
Reviewed-on: https://chromium-review.googlesource.com/204391
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>
diff --git a/debugd/src/process_with_id.h b/debugd/src/process_with_id.h
index 527e5fc..65d0cef 100644
--- a/debugd/src/process_with_id.h
+++ b/debugd/src/process_with_id.h
@@ -2,8 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef PROCESS_WITH_ID_H
-#define PROCESS_WITH_ID_H
+#ifndef PROCESS_WITH_ID_H_
+#define PROCESS_WITH_ID_H_
+
+#include <string>
 
 #include "sandboxed_process.h"
 
@@ -17,12 +19,13 @@
  public:
   ProcessWithId();
   virtual bool Init();
-  std::string id() const { return id_; }
+  const std::string& id() const { return id_; }
+
  private:
-  bool generate_id();
+  bool GenerateId();
   std::string id_;
 };
 
-};  // namespace debugd
+}  // namespace debugd
 
-#endif  // PROCESS_WITH_ID_H
+#endif  // PROCESS_WITH_ID_H_