[v8] Add feature flag for --sparkplug-needs-short-builtins

Change-Id: Ic3df96c39ddff116c5cd45216689b30ca21c03bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2988760
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jeremy Roman <jbroman@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#896083}

gin/gin_features.cc

@@ -63,6 +63,11 @@ const base::Feature kV8Turboprop{"V8Turboprop",
 const base::Feature kV8Sparkplug{"V8Sparkplug",
                                  base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Makes sure the experimental Sparkplug compiler is only enabled if short
+// builtin calls are enabled too.
+const base::Feature kV8SparkplugNeedsShortBuiltinCalls{
+    "V8SparkplugNeedsShortBuiltinCalls", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables short builtin calls feature.
 const base::Feature kV8ShortBuiltinCalls{"V8ShortBuiltinCalls",
                                          base::FEATURE_ENABLED_BY_DEFAULT};

gin/gin_features.h

@@ -26,6 +26,7 @@ GIN_EXPORT extern const base::Feature kV8ExperimentalRegexpEngine;
 GIN_EXPORT extern const base::Feature kV8TurboFastApiCalls;
 GIN_EXPORT extern const base::Feature kV8Turboprop;
 GIN_EXPORT extern const base::Feature kV8Sparkplug;
+GIN_EXPORT extern const base::Feature kV8SparkplugNeedsShortBuiltinCalls;
 GIN_EXPORT extern const base::Feature kV8ScriptAblation;
 GIN_EXPORT extern const base::FeatureParam<int> kV8ScriptDelayOnceMs;
 GIN_EXPORT extern const base::FeatureParam<int> kV8ScriptDelayMs;

gin/v8_initializer.cc

@@ -325,6 +325,11 @@ void V8Initializer::Initialize(IsolateHolder::ScriptMode mode) {
     SetV8Flags("--sparkplug");
   }
 
+  if (base::FeatureList::IsEnabled(
+          features::kV8SparkplugNeedsShortBuiltinCalls)) {
+    SetV8Flags("--sparkplug-needs-short-builtins");
+  }
+
   if (base::FeatureList::IsEnabled(features::kV8UntrustedCodeMitigations)) {
     SetV8Flags("--untrusted-code-mitigations");
   } else {