Share field trial allocator on zygote-using Linuxes

content/app/content_main_runner.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 "content/public/app/content_main_runner.h"
 
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ skipping 126 matching lines @@
       *base::CommandLine::ForCurrentProcess();
 
   // Initialize statistical testing infrastructure.  We set the entropy
   // provider to nullptr to disallow non-browser processes from creating
   // their own one-time randomized trials; they should be created in the
   // browser process.
   field_trial_list->reset(new base::FieldTrialList(nullptr));
 
   // Ensure any field trials in browser are reflected into the child
   // process.
+#if defined(OS_POSIX)
+  // On POSIX systems that use the zygote, we get the trials from a shared
+  // memory segment backed by an fd instead of the command line.
   base::FieldTrialList::CreateTrialsFromCommandLine(
-      command_line, switches::kFieldTrialHandle);
+      command_line, switches::kFieldTrialHandle, kFieldTrialDescriptor);
+#else
+  base::FieldTrialList::CreateTrialsFromCommandLine(
+      command_line, switches::kFieldTrialHandle, -1);
+#endif
 
   std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
   feature_list->InitializeFromCommandLine(
       command_line.GetSwitchValueASCII(switches::kEnableFeatures),
       command_line.GetSwitchValueASCII(switches::kDisableFeatures));
   base::FeatureList::SetInstance(std::move(feature_list));
 }
 
 }  // namespace
 
@@ skipping 312 matching lines @@
     // - The ipc_fd is passed through the Java service.
     // Thus, these are all disabled.
 #if !defined(OS_ANDROID)
     // Set C library locale to make sure CommandLine can parse argument values
     // in correct encoding.
     setlocale(LC_ALL, "");
 
     SetupSignalHandlers();
     g_fds->Set(kMojoIPCChannel,
                kMojoIPCChannel + base::GlobalDescriptors::kBaseDescriptor);
+
+    g_fds->Set(
+        kFieldTrialDescriptor,
+        kFieldTrialDescriptor + base::GlobalDescriptors::kBaseDescriptor);
 #endif  // !OS_ANDROID
 
 #if defined(OS_LINUX) || defined(OS_OPENBSD)
     g_fds->Set(kCrashDumpSignal,
                kCrashDumpSignal + base::GlobalDescriptors::kBaseDescriptor);
 #endif  // OS_LINUX || OS_OPENBSD
 
 
 #endif  // !OS_WIN
 
@@ skipping 340 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(ContentMainRunnerImpl);
 };
 
 // static
 ContentMainRunner* ContentMainRunner::Create() {
   return new ContentMainRunnerImpl();
 }
 
 }  // namespace content