Store and retrieve features from shared memory

base/metrics/field_trial_unittest.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 <stddef.h>
 
 #include "base/base_switches.h"
 #include "base/build_time.h"
@@ skipping 1127 matching lines @@
 }
 
 #if defined(OS_WIN)
 TEST(FieldTrialListTest, TestCopyFieldTrialStateToFlags) {
   base::FieldTrialList field_trial_list(
       base::MakeUnique<base::MockEntropyProvider>());
   base::FieldTrialList::CreateFieldTrial("Trial1", "Group1");
   base::FilePath test_file_path = base::FilePath(FILE_PATH_LITERAL("Program"));
   base::CommandLine cmd_line = base::CommandLine(test_file_path);
   const char field_trial_handle[] = "test-field-trial-handle";
+  const char enable_features_switch[] = "test-enable-features";
+  const char disable_features_switch[] = "test-disable-features";
 
-  base::FieldTrialList::CopyFieldTrialStateToFlags(field_trial_handle,
-                                                   &cmd_line);
+  base::FieldTrialList::CopyFieldTrialStateToFlags(
+      field_trial_handle, enable_features_switch, disable_features_switch,
+      &cmd_line);
   EXPECT_TRUE(cmd_line.HasSwitch(field_trial_handle) ||
               cmd_line.HasSwitch(switches::kForceFieldTrials));
 }
 #endif
 
+#if !defined(OS_IOS)
 TEST(FieldTrialListTest, InstantiateAllocator) {
+  std::unique_ptr<FeatureList> feature_list(new FeatureList);

[Alexei Svitkine (slow), 2016/12/02 20:14:28]

This doesn't actually register the instance. (It doesn't work same way as
FieldTrialList.)

Can you use ScopedFeatureList here?

[lawrencewu, 2016/12/02 20:36:32]

Done. This also turned out to be the cause of those iossim crashes (the
singleton was null).

+
   FieldTrialList field_trial_list(nullptr);
   FieldTrialList::CreateFieldTrial("Trial1", "Group1");
 
   FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();
   void* memory = field_trial_list.field_trial_allocator_->shared_memory();
   size_t used = field_trial_list.field_trial_allocator_->used();
 
   // Ensure that the function is idempotent.
   FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded();
   void* new_memory = field_trial_list.field_trial_allocator_->shared_memory();
   size_t new_used = field_trial_list.field_trial_allocator_->used();
   EXPECT_EQ(memory, new_memory);
   EXPECT_EQ(used, new_used);
 }
+#endif
 
 TEST(FieldTrialListTest, AddTrialsToAllocator) {
   std::string save_string;
   base::SharedMemoryHandle handle;
 
   // Scoping the first FieldTrialList, as we need another one to test that it
   // matches.
   {
     FieldTrialList field_trial_list(nullptr);
     FieldTrialList::CreateFieldTrial("Trial1", "Group1");
@@ skipping 120 matching lines @@
   std::unique_ptr<base::SharedMemory> shm(new SharedMemory(handle, true));
   // 4 KiB is enough to hold the trials only created for this test.
   shm.get()->Map(4 << 10);
   FieldTrialList::CreateTrialsFromSharedMemory(std::move(shm));
   std::string check_string;
   FieldTrialList::AllStatesToString(&check_string);
   EXPECT_EQ("*Trial1/Group1/", check_string);
 }
 
 }  // namespace base