Fix field trials not working in utility processes.

base/metrics/field_trial.cc

 // 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.
 
 #include "base/metrics/field_trial.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/base_switches.h"
 #include "base/build_time.h"
 #include "base/command_line.h"
 #include "base/debug/activity_tracker.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial_param_associator.h"
 #include "base/process/memory.h"
+#include "base/process/process_handle.h"
+#include "base/process/process_info.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/unguessable_token.h"
 
 // On POSIX, the fd is shared using the mapping in GlobalDescriptors.
 #if defined(OS_POSIX) && !defined(OS_NACL)
@@ skipping 1108 matching lines @@
   std::vector<base::StringPiece> tokens = base::SplitStringPiece(
       switch_value, ",", base::KEEP_WHITESPACE, base::SPLIT_WANT_ALL);
 
   if (tokens.size() != 4)
     return SharedMemoryHandle();
 
   int field_trial_handle = 0;
   if (!base::StringToInt(tokens[0], &field_trial_handle))
     return SharedMemoryHandle();
   RawHandle handle = reinterpret_cast<RawHandle>(field_trial_handle);
+#if defined(OS_WIN)
+  if (base::IsCurrentProcessElevated()) {
+    // base::LaunchElevatedProcess doesn't have a way to duplicate the handle,
+    // but this process can since by definition it's not sandboxed.
+    base::ProcessId parent_pid = base::GetParentProcessId(GetCurrentProcess());
+    HANDLE parent_handle = OpenProcess(PROCESS_ALL_ACCESS, FALSE, parent_pid);
+    DuplicateHandle(parent_handle, handle, GetCurrentProcess(), &handle, 0,
+                    FALSE, DUPLICATE_SAME_ACCESS);
+    CloseHandle(parent_handle);
+  }

[(unused - use chromium), 2017/06/30 16:15:18]

Having OS-dependent elevantion-level-dependent code in base/metrics seems a tad
questionable to me, but I guess a base/metrics/OWNER already approved this
part.. :-P

[Alexei Svitkine (slow), 2017/06/30 16:20:37]

I agree this is not ideal. But I don't have a suggestion of how this could be
done better. Do you have a suggestion?

+#endif
 
   base::UnguessableToken guid;
   if (!DeserializeGUIDFromStringPieces(tokens[1], tokens[2], &guid))
     return SharedMemoryHandle();
 
   int size;
   if (!base::StringToInt(tokens[3], &size))
     return SharedMemoryHandle();
 
   return SharedMemoryHandle(handle, static_cast<size_t>(size), guid);
@@ skipping 260 matching lines @@
     return;
   }
   AutoLock auto_lock(global_->lock_);
   CHECK(!global_->PreLockedFind(trial->trial_name())) << trial->trial_name();
   trial->AddRef();
   trial->SetTrialRegistered();
   global_->registered_[trial->trial_name()] = trial;
 }
 
 }  // namespace base