Pass file Regions along with FDs to child processes on Android

base/files/memory_mapped_file.h

Index: base/files/memory_mapped_file.h
diff --git a/base/files/memory_mapped_file.h b/base/files/memory_mapped_file.h
index 8a7f045f351a0365d496f37f5824607cacfdc12e..c0fcd3862ad2e315661e799556e022a06627f93d 100644
--- a/base/files/memory_mapped_file.h
+++ b/base/files/memory_mapped_file.h
@@ -28,6 +28,7 @@ class BASE_EXPORT MemoryMappedFile {
   struct BASE_EXPORT Region {
     static const Region kWholeFile;
 
+    Region();

[agrieve, 2015/05/28 17:26:23]

Note: Need this so Region can be used in std::Map, and so it's less annoying to
have one as a member of a class. 

There is no place where kWholeFile has its address taken, so there is no need
for it to be the unique (0,0) instance. Having no default ctor also doesn't
ensure uniqueness since |offset| and |size| are public non-const.

     Region(int64 offset, int64 size);
 
     bool operator==(const Region& other) const;
@@ -39,8 +40,7 @@ class BASE_EXPORT MemoryMappedFile {
     int64 size;
 
    private:
-    // This ctor is used only by kWholeFile, to construct a zero-sized Region
-    // (which is forbidden by the public ctor) and uniquely identify kWholeFile.
+    // This ctor is used only by kWholeFile, to construct kWholeFile.
     Region(base::LinkerInitialized);
   };