Add feature flag for launch_handler manifest field

Intent to prototype:
https://groups.google.com/a/chromium.org/g/blink-dev/c/8tNe2jrJ78A

Bug: 1231886
Change-Id: Id7c7a34c140c8932798af5dea5dab12e4a2e4c09
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3068785
Commit-Queue: Alan Cutter <[email protected]>
Reviewed-by: Nate Chapin <[email protected]>
Cr-Commit-Position: refs/heads/master@{#908770}

Author: alancutter

content/child/runtime_features.cc

@@ -395,6 +395,7 @@ void SetRuntimeFeaturesFromChromiumFeatures() {
                kThrottleDisplayNoneAndVisibilityHiddenCrossOriginIframes},
           {"TrustedDOMTypes", features::kTrustedDOMTypes},
           {"UserAgentClientHint", blink::features::kUserAgentClientHint},
+          {"WebAppLaunchHandler", blink::features::kWebAppEnableLaunchHandler},
           {"WebAppLinkCapturing", blink::features::kWebAppEnableLinkCapturing},
           {"WebAppTabStrip", features::kDesktopPWAsTabStrip},
           {"WebAppWindowControlsOverlay",

third_party/blink/common/features.cc

@@ -849,6 +849,11 @@ const base::Feature kLogUnexpectedIPCPostedToBackForwardCachedDocuments{
 const base::Feature kWebAppEnableIsolatedStorage{
     "WebAppEnableIsolatedStorage", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables the "launch_handler" manifest field for web apps.
+// Explainer: https://github.com/WICG/sw-launch/blob/main/launch_handler.md
+const base::Feature kWebAppEnableLaunchHandler{
+    "WebAppEnableLaunchHandler", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables declarative link capturing in web apps.
 // Explainer:
 // https://github.com/WICG/sw-launch/blob/master/declarative_link_capturing.md

third_party/blink/public/common/features.h

@@ -341,6 +341,8 @@ BLINK_COMMON_EXPORT extern const base::Feature
 
 BLINK_COMMON_EXPORT extern const base::Feature kWebAppEnableIsolatedStorage;
 
+BLINK_COMMON_EXPORT extern const base::Feature kWebAppEnableLaunchHandler;
+
 BLINK_COMMON_EXPORT extern const base::Feature kWebAppEnableLinkCapturing;
 
 BLINK_COMMON_EXPORT extern const base::Feature kWebAppEnableManifestId;

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -2276,6 +2276,10 @@
       name: "WebAnimationsSVG",
       status: "experimental",
     },
+    {
+      name: "WebAppLaunchHandler",
+      status: "experimental",
+    },
     {
       name: "WebAppLinkCapturing",
       origin_trial_feature_name: "WebAppLinkCapturing",