Multiprocess test client: Android child process launcher rework.

base/posix/global_descriptors.cc

Index: base/posix/global_descriptors.cc
diff --git a/base/posix/global_descriptors.cc b/base/posix/global_descriptors.cc
index 6c187838ad69d63051a1155d64c26623de8a2db0..815250809184f28f01acc84ceecac192ede77f4a 100644
--- a/base/posix/global_descriptors.cc
+++ b/base/posix/global_descriptors.cc
@@ -8,6 +8,7 @@
 #include <utility>
 
 #include "base/logging.h"
+#include "base/rand_util.h"
 
 namespace base {
 
@@ -65,6 +66,16 @@ void GlobalDescriptors::Set(Key key,
   descriptors_.push_back(Descriptor(key, fd, region));
 }
 
+GlobalDescriptors::Key GlobalDescriptors::Register(int fd) {
+  // Find a random unused key.
+  Key key;
+  do {
+    base::RandBytes(&key, sizeof(Key));
+  } while (MaybeGet(key) != -1);
+  Set(key, fd);
+  return key;
+}
+
 base::MemoryMappedFile::Region GlobalDescriptors::GetRegion(Key key) const {
   for (const auto& i : descriptors_) {
     if (i.key == key)