Add flag for SignedExchangeSubresourcePrefetch

Bug: 935267
Change-Id: Ic2d1a181a3592262c30b755cf34d3d7bda71f45b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1527949Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642434}

content/child/runtime_features.cc

@@ -495,6 +495,10 @@ void SetIndividualRuntimeFeatures(
 
   if (base::FeatureList::IsEnabled(features::kUserAgentClientHint))
     WebRuntimeFeatures::EnableFeatureFromString("UserAgentClientHint", true);
+
+  WebRuntimeFeatures::EnableSignedExchangeSubresourcePrefetch(
+      base::FeatureList::IsEnabled(
+          features::kSignedExchangeSubresourcePrefetch));
 }
 
 }  // namespace

content/public/common/content_features.cc

@@ -463,6 +463,11 @@ const base::Feature kSharedArrayBuffer {
 const base::Feature kSignedExchangeReportingForDistributors{
     "SignedExchangeReportingForDistributors", base::FEATURE_ENABLED_BY_DEFAULT};
 
+// Subresource prefetching+loading via Signed HTTP Exchange
+// https://www.chromestatus.com/features/5126805474246656
+const base::Feature kSignedExchangeSubresourcePrefetch{
+    "SignedExchangeSubresourcePrefetch", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Origin-Signed HTTP Exchanges (for WebPackage Loading)
 // https://www.chromestatus.com/features/5745285984681984
 const base::Feature kSignedHTTPExchange{"SignedHTTPExchange",

content/public/common/content_features.h

@@ -108,6 +108,7 @@ CONTENT_EXPORT extern const base::Feature kServiceWorkerPaymentApps;
 CONTENT_EXPORT extern const base::Feature kSharedArrayBuffer;
 CONTENT_EXPORT extern const base::Feature
     kSignedExchangeReportingForDistributors;
+CONTENT_EXPORT extern const base::Feature kSignedExchangeSubresourcePrefetch;
 CONTENT_EXPORT extern const base::Feature kSignedHTTPExchange;
 CONTENT_EXPORT extern const base::Feature kSkipBrowserTouchFilter;
 CONTENT_EXPORT extern const char kSkipBrowserTouchFilterTypeParamName[];

third_party/blink/public/platform/web_runtime_features.h

@@ -237,6 +237,8 @@ class WebRuntimeFeatures {
   BLINK_PLATFORM_EXPORT static void EnableShadowDOMV0(bool);
   BLINK_PLATFORM_EXPORT static void EnableCustomElementsV0(bool);
   BLINK_PLATFORM_EXPORT static void EnableHTMLImports(bool);
+  BLINK_PLATFORM_EXPORT static void EnableSignedExchangeSubresourcePrefetch(
+      bool);
 
  private:
   WebRuntimeFeatures();

third_party/blink/renderer/platform/exported/web_runtime_features.cc

@@ -657,4 +657,8 @@ void WebRuntimeFeatures::EnableHTMLImports(bool enable) {
   RuntimeEnabledFeatures::SetHTMLImportsOnlyChromeEnabled(enable);
 }
 
+void WebRuntimeFeatures::EnableSignedExchangeSubresourcePrefetch(bool enable) {
+  RuntimeEnabledFeatures::SetSignedExchangeSubresourcePrefetchEnabled(enable);
+}
+
 }  // namespace blink

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -1316,6 +1316,9 @@
       origin_trial_feature_name: "SignatureBasedIntegrity",
       status: "experimental",
     },
+    {
+      name: "SignedExchangeSubresourcePrefetch",
+    },
     {
       name: "SkipAd",
       depends_on: ["MediaSession"],