Revert of Multiprocess test client: Android child process launcher rework.

base/posix/global_descriptors.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 BASE_POSIX_GLOBAL_DESCRIPTORS_H_
 #define BASE_POSIX_GLOBAL_DESCRIPTORS_H_
 
 #include "build/build_config.h"
 
 #include <vector>
@@ skipping 34 matching lines @@
     Key key;
     // Actual FD.
     int fd;
     // Optional region, defaults to kWholeFile.
     base::MemoryMappedFile::Region region;
   };
   typedef std::vector<Descriptor> Mapping;
 
   // Often we want a canonical descriptor for a given Key. In this case, we add
   // the following constant to the key value:
+#if !defined(OS_ANDROID)
   static const int kBaseDescriptor = 3;  // 0, 1, 2 are already taken.
+#else
+  // 3 used by __android_log_write().
+  // 4 used by... something important on Android M.
+  // 5 used by... something important on Android L... on low-end devices.
+  // TODO(amistry): An Android, this mechanism is only used for tests since the
+  // content child launcher spawns a process by creating a new Activity using
+  // the Android APIs. For tests, come up with a way that doesn't require using
+  // a pre-defined fd.
+  static const int kBaseDescriptor = 6;
+#endif
 
   // Return the singleton instance of GlobalDescriptors.
   static GlobalDescriptors* GetInstance();
 
   // Get a descriptor given a key. It is a fatal error if the key is not known.
   int Get(Key key) const;
 
   // Get a descriptor given a key. Returns -1 on error.
   int MaybeGet(Key key) const;
 
@@ skipping 13 matching lines @@
   friend struct DefaultSingletonTraits<GlobalDescriptors>;
   GlobalDescriptors();
   ~GlobalDescriptors();
 
   Mapping descriptors_;
 };
 
 }  // namespace base
 
 #endif  // BASE_POSIX_GLOBAL_DESCRIPTORS_H_