feat: initialize field trials from command line arguments (#28402)

Fixes: #27877

Co-authored-by: Saúl Ibarra Corretgé <s@saghul.net>

shell/browser/electron_browser_main_parts.cc

@@ -279,6 +279,9 @@ void ElectronBrowserMainParts::PostEarlyInitialization() {
   base::FeatureList::ClearInstanceForTesting();
   InitializeFeatureList();
 
+  // Initialize field trials.
+  InitializeFieldTrials();
+
   // Initialize after user script environment creation.
   fake_browser_process_->PostEarlyInitialization();
 }

shell/browser/feature_list.cc

@@ -9,6 +9,7 @@
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/feature_list.h"
+#include "base/metrics/field_trial.h"
 #include "content/public/common/content_features.h"
 #include "electron/buildflags/buildflags.h"
 #include "media/base/media_switches.h"
@@ -49,4 +50,12 @@ void InitializeFeatureList() {
   base::FeatureList::InitializeInstance(enable_features, disable_features);
 }
 
+void InitializeFieldTrials() {
+  auto* cmd_line = base::CommandLine::ForCurrentProcess();
+  auto force_fieldtrials =
+      cmd_line->GetSwitchValueASCII(::switches::kForceFieldTrials);
+
+  base::FieldTrialList::CreateTrialsFromString(force_fieldtrials);
+}
+
 }  // namespace electron

shell/browser/feature_list.h

@@ -7,6 +7,7 @@
 
 namespace electron {
 void InitializeFeatureList();
-}
+void InitializeFieldTrials();
+}  // namespace electron
 
 #endif  // SHELL_BROWSER_FEATURE_LIST_H_