Initial implementation for sharing field trial state (win)

content/app/content_main_runner.cc

Index: content/app/content_main_runner.cc
diff --git a/content/app/content_main_runner.cc b/content/app/content_main_runner.cc
index 01bb5f00f42ce6a9499708f7a53c5766054c62fc..69c1234d38e125e364a6629bb696293abdace9b5 100644
--- a/content/app/content_main_runner.cc
+++ b/content/app/content_main_runner.cc
@@ -26,12 +26,14 @@
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/scoped_vector.h"
+#include "base/memory/shared_memory.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/path_service.h"
 #include "base/process/launch.h"
 #include "base/process/memory.h"
+#include "base/process/process.h"
 #include "base/process/process_handle.h"
 #include "base/profiler/scoped_tracker.h"
 #include "base/strings/string_number_conversions.h"
@@ -146,7 +148,25 @@ void InitializeFieldTrialAndFeatureList(
 
   // Ensure any field trials in browser are reflected into the child
   // process.
-  if (command_line.HasSwitch(switches::kForceFieldTrials)) {
+  if (command_line.HasSwitch(switches::kFieldTrialHandle)) {
+    std::string arg =
+        command_line.GetSwitchValueASCII(switches::kFieldTrialHandle);
+    size_t token = arg.find(",");
+    int field_trial_handle = std::stoi(arg.substr(0, token));
+    int field_trial_length = std::stoi(arg.substr(token + 1, arg.length()));
+
+    HANDLE handle = reinterpret_cast<HANDLE>(field_trial_handle);
+    base::SharedMemoryHandle shm_handle =
+        base::SharedMemoryHandle(handle, base::GetCurrentProcId());
+
+    base::SharedMemory shared_memory(shm_handle, false);
+    shared_memory.Map(field_trial_length);
+
+    char* field_trial_state = static_cast<char*>(shared_memory.memory());
+    bool result = base::FieldTrialList::CreateTrialsFromString(
+        std::string(field_trial_state), std::set<std::string>());
+    DCHECK(result);
+  } else if (command_line.HasSwitch(switches::kForceFieldTrials)) {
     bool result = base::FieldTrialList::CreateTrialsFromString(
         command_line.GetSwitchValueASCII(switches::kForceFieldTrials),
         std::set<std::string>());