Files required by a service now listed in manifest.

base/file_descriptor_store.h

+// Copyright 2017 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 BASE_FILE_DESCRIPTOR_STORE_H_
+#define BASE_FILE_DESCRIPTOR_STORE_H_
+
+#include <map>
+#include <string>
+
+#include "base/files/memory_mapped_file.h"
+#include "base/files/scoped_file.h"
+#include "base/macros.h"
+
+namespace base {
+
+// The file descriptor store is used to associate file descriptors with keys
+// that must be unique.
+// It is used to share file descriptors from a process to its child.

[dcheng, 2017/02/10 08:44:15]

Can we just change GlobalDescriptors to have the desired interface in a separate
patch, rather than adding a new thing?

[Jay Civelli, 2017/02/13 18:48:25]

It's going to be quite a bit of work to change to process start-up to use the
new interface in all cases.
This patch is the first one toward that goal.
When we get there, the GlobalDescriptors class will go away altogether. It's
probably easier during the transition to keep both classes separate.

+class BASE_EXPORT FileDescriptorStore {
+ public:
+  struct Descriptor {
+    Descriptor(const std::string& key, base::ScopedFD fd);
+    Descriptor(const std::string& key,
+               base::ScopedFD fd,
+               base::MemoryMappedFile::Region region);
+    Descriptor(Descriptor&& other);
+    ~Descriptor();
+
+    Descriptor& operator=(Descriptor&& other);
+
+    // Globally unique key.
+    std::string key;
+    // Actual FD.
+    base::ScopedFD fd;
+    // Optional region, defaults to kWholeFile.
+    base::MemoryMappedFile::Region region;
+  };
+  using Mapping = std::map<std::string, Descriptor>;
+
+  // Returns the singleton instance of FileDescriptorStore.
+  static FileDescriptorStore& GetInstance();
+
+  // Gets a descriptor given a key and also populates |region| if non null.
+  // It is a fatal error if the key is not known.
+  base::ScopedFD TakeFD(const std::string& key,
+                        base::MemoryMappedFile::Region* region);
+
+  // Gets a descriptor given a key. Returns an empty ScopedFD on error.
+  base::ScopedFD MaybeTakeFD(const std::string& key,
+                             base::MemoryMappedFile::Region* region);
+
+  // Sets the descriptor for the given |key|. This sets the region associated
+  // with |key| to kWholeFile.
+  void Set(const std::string& key, base::ScopedFD fd);
+
+  // Sets the descriptor and |region| for the given |key|.
+  void Set(const std::string& key,
+           base::ScopedFD fd,
+           base::MemoryMappedFile::Region region);
+
+ private:
+  FileDescriptorStore();
+  ~FileDescriptorStore();
+
+  Mapping descriptors_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileDescriptorStore);
+};
+
+}  // namespace base
+
+#endif  // BASE_FILE_DESCRIPTOR_STORE_H_