Remove PRODUCT_STRING_PATH from chrome_constants.h on Windows.

components/browser_watcher/exit_code_watcher_win.h

 // Copyright (c) 2014 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.
 #ifndef COMPONENTS_BROWSER_WATCHER_EXIT_CODE_WATCHER_WIN_H_
 #define COMPONENTS_BROWSER_WATCHER_EXIT_CODE_WATCHER_WIN_H_
 
 #include "base/macros.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
+#include "base/strings/string_piece.h"
 #include "base/time/time.h"
 #include "base/win/scoped_handle.h"
 
 namespace browser_watcher {
 
 // Watches for the exit code of a process and records it in a given registry
 // location.
 class ExitCodeWatcher {
  public:
   // Initialize the watcher with a registry path.
-  explicit ExitCodeWatcher(const base::char16* registry_path);
+  explicit ExitCodeWatcher(base::StringPiece16 registry_path);
   ~ExitCodeWatcher();
 
   // Initializes from arguments on |cmd_line|, returns true on success.
   // This function expects |process| to be open with sufficient privilege to
   // wait and retrieve the process exit code.
   // It checks the handle for validity and takes ownership of it.
   // The intent is for this handle to be inherited into the watcher process
   // hosting the instance of this class.
   bool Initialize(base::Process process);
 
   // Waits for the process to exit and records its exit code in registry.
   // This is a blocking call.
   void WaitForExit();
 
   const base::Process& process() const { return process_; }
   int exit_code() const { return exit_code_; }
 
  private:
   // Writes |exit_code| to registry, returns true on success.
   bool WriteProcessExitCode(int exit_code);
 
   // The registry path the exit codes are written to.
-  base::string16 registry_path_;
+  const base::string16 registry_path_;
 
   // Watched process and its creation time.
   base::Process process_;
   base::Time process_creation_time_;
 
   // The exit code of the watched process. Valid after WaitForExit.
   int exit_code_;
 
   DISALLOW_COPY_AND_ASSIGN(ExitCodeWatcher);
 };
 
 }  // namespace browser_watcher
 
 #endif  // COMPONENTS_BROWSER_WATCHER_EXIT_CODE_WATCHER_WIN_H_