Simplifying ContentBrowserClient::GetAdditionalMappedFiles...()

content/public/browser/file_descriptor_info.h

 // Copyright (c) 2012 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 CONTENT_PUBLIC_BROWSER_FILE_DESCRIPTOR_INFO_H_
 #define CONTENT_PUBLIC_BROWSER_FILE_DESCRIPTOR_INFO_H_
 
 #include <stddef.h>
 
 #include "base/files/file.h"
+#include "base/files/memory_mapped_file.h"
 #include "base/process/launch.h"
 
 namespace content {
 
-// FileDescriptorInfo is a collection of file descriptors which is
-// needed to launch a process. You should tell FileDescriptorInfo
-// which FD should be closed and which shouldn't so that it can take care
-// of the lifetime of FDs.
+// FileDescriptorInfo is a collection of file descriptors which is needed to
+// launch a process. You should tell FileDescriptorInfo which FDs should be
+// closed and which shouldn't so that it can take care of the lifetime of FDs.
 //
-// See base/process/launcher.h for more details about launching a
-// process.
+// See base/process/launcher.h for more details about launching a process.
 class FileDescriptorInfo {
  public:
   virtual ~FileDescriptorInfo() {}
 
-  // Add an FD associated with an ID, without delegating the ownerhip
-  // of ID.
+  // Adds an FD associated with an ID, without delegating the ownerhip of ID.
   virtual void Share(int id, base::PlatformFile fd) = 0;
 
-  // Add an FD associated with an ID, passing the FD ownership to
+  // Similar to Share but also provides a region in that file that should be
+  // read in the launched process (accessible with GetRegionAt()).
+  virtual void ShareWithRegion(int id, base::PlatformFile fd,

[jam, 2017/01/06 01:28:45]

nit: indentation is off per style guide. if the second line doesn't align with
"int id", then move the "int id" to the next line

+      const base::MemoryMappedFile::Region& region) = 0;
+
+  // Adds an FD associated with an ID, passing the FD ownership to
   // FileDescriptorInfo.
   virtual void Transfer(int id, base::ScopedFD fd) = 0;
 
-  // A vecotr backed map of registered ID-FD pairs.
+  // A vector backed map of registered ID-FD pairs.
   virtual const base::FileHandleMappingVector& GetMapping() const = 0;
 
-  // A GetMapping() variant what adjusts the ID value by |delta|.
+  // A GetMapping() variant that adjusts the ID value by |delta|.
   // Some environments need this trick.
   virtual base::FileHandleMappingVector GetMappingWithIDAdjustment(
       int delta) const = 0;
 
-  // API for iterating registered ID-FD pairs.
+  // API for iterating over the registered ID-FD pairs.
   virtual base::PlatformFile GetFDAt(size_t i) const = 0;
   virtual int GetIDAt(size_t i) const = 0;
+  virtual const base::MemoryMappedFile::Region& GetRegionAt(size_t i) const = 0;
   virtual size_t GetMappingSize() const = 0;
 
-  // True if |this| has an ownership of |file|.
+  // Returns true if |this| has ownership of |file|.
   virtual bool OwnsFD(base::PlatformFile file) const = 0;
-  // Assuming |OwnsFD(file)|, release the ownership.
+  // Assuming |OwnsFD(file)|, releases the ownership.
   virtual base::ScopedFD ReleaseFD(base::PlatformFile file) = 0;
 };
 
 }
 
 #endif  // CONTENT_PUBLIC_BROWSER_FILE_DESCRIPTOR_INFO_H_