Store and retrieve features from shared memory

base/metrics/field_trial.cc

Index: base/metrics/field_trial.cc
diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc
index ee1629c2e55c40bf343f1e5f9db48f598c95e36d..6f251c0fb7ffc0724e968f07d47e3e2c3276b758 100644
--- a/base/metrics/field_trial.cc
+++ b/base/metrics/field_trial.cc
@@ -10,7 +10,6 @@
 #include "base/base_switches.h"
 #include "base/build_time.h"
 #include "base/command_line.h"
-#include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/pickle.h"
 #include "base/process/memory.h"
@@ -184,7 +183,19 @@ bool ParseFieldTrialsString(const std::string& trials_string,
   return true;
 }
 
-void AddForceFieldTrialsFlag(CommandLine* cmd_line) {
+void AddFeatureAndFieldTrialFlags(CommandLine* cmd_line,

[Alexei Svitkine (slow), 2016/12/01 19:39:22]

Nit: Non-const params should be last.

[lawrencewu, 2016/12/02 19:24:46]

Done.

+                                  const char* enable_features_switch,
+                                  const char* disable_features_switch) {
+  std::string enabled_features;
+  std::string disabled_features;
+  FeatureList::GetInstance()->GetFeatureOverrides(&enabled_features,
+                                                  &disabled_features);
+
+  if (!enabled_features.empty())
+    cmd_line->AppendSwitchASCII(enable_features_switch, enabled_features);
+  if (!disabled_features.empty())
+    cmd_line->AppendSwitchASCII(disable_features_switch, disabled_features);
+
   std::string field_trial_states;
   FieldTrialList::AllStatesToString(&field_trial_states);
   if (!field_trial_states.empty()) {
@@ -741,6 +752,22 @@ void FieldTrialList::CreateTrialsFromCommandLine(
   }
 }
 
+// static
+void FieldTrialList::CreateFeaturesFromCommandLine(
+    const base::CommandLine& command_line,
+    const char* enable_features_switch,
+    const char* disable_features_switch,
+    std::unique_ptr<FeatureList>& feature_list) {

[Alexei Svitkine (slow), 2016/12/01 19:39:22]

Don't pass non const refs.

You can pass as a FeatureList*

[lawrencewu, 2016/12/02 19:24:46]

Done.

+  // Fallback to command line if not using shared memory.
+  if (!kUseSharedMemoryForFieldTrials || !global_->field_trial_allocator_.get())

[Alexei Svitkine (slow), 2016/12/01 19:39:22]

Nit: {}'s

+    return feature_list->InitializeFromCommandLine(
+        command_line.GetSwitchValueASCII(enable_features_switch),
+        command_line.GetSwitchValueASCII(disable_features_switch));
+
+  feature_list->InitializeFromSharedMemory(
+      global_->field_trial_allocator_.get());
+}
+
 #if defined(POSIX_WITH_ZYGOTE)
 // static
 bool FieldTrialList::CreateTrialsFromDescriptor(int fd_key) {
@@ -790,6 +817,8 @@ int FieldTrialList::GetFieldTrialHandle() {
 // static
 void FieldTrialList::CopyFieldTrialStateToFlags(
     const char* field_trial_handle_switch,
+    const char* enable_features_switch,
+    const char* disable_features_switch,
     CommandLine* cmd_line) {
   // TODO(lawrencewu): Ideally, having the global would be guaranteed. However,
   // content browser tests currently don't create a FieldTrialList because they
@@ -805,7 +834,8 @@ void FieldTrialList::CopyFieldTrialStateToFlags(
     // If the readonly handle didn't get duplicated properly, then fallback to
     // original behavior.
     if (global_->readonly_allocator_handle_ == kInvalidPlatformFile) {
-      AddForceFieldTrialsFlag(cmd_line);
+      AddFeatureAndFieldTrialFlags(cmd_line, enable_features_switch,
+                                   disable_features_switch);
       return;
     }
 
@@ -831,7 +861,8 @@ void FieldTrialList::CopyFieldTrialStateToFlags(
   }
 #endif
 
-  AddForceFieldTrialsFlag(cmd_line);
+  AddFeatureAndFieldTrialFlags(cmd_line, enable_features_switch,
+                               disable_features_switch);
 }
 
 // static
@@ -1007,6 +1038,10 @@ void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() {
     AddToAllocatorWhileLocked(registered.second);
   }
 
+  // Add all existing features.
+  FeatureList::GetInstance()->AddFeaturesToAllocator(
+      global_->field_trial_allocator_.get());
+
 #if defined(OS_WIN) || defined(POSIX_WITH_ZYGOTE)
   // Set |readonly_allocator_handle_| so we can pass it to be inherited and
   // via the command line.