[WebNFC] Enable feature flag by default for Origin Trial

For the WebNFC Origin Trial the feature flag needs to be enabled by
default and configured as "disable only" in runtime_features.cc so that
it can still be used as a kill switch but will not enable the feature
on sites which don't have a valid Origin Trial token.

Bug: 1035048
Change-Id: I139a79dd0f93013bc59d5023017b49c820532fb1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2052198
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743309}

content/child/runtime_features.cc

@@ -99,11 +99,6 @@ void SetRuntimeFeatureDefaultsForPlatform(
     WebRuntimeFeatures::EnableMediaSession(false);
 #endif
 
-#if defined(OS_ANDROID)
-  WebRuntimeFeatures::EnableWebNfc(
-      base::FeatureList::IsEnabled(features::kWebNfc));
-#endif
-
 #if defined(OS_ANDROID)
   // APIs for Web Authentication are not available prior to N.
   WebRuntimeFeatures::EnableWebAuth(
@@ -310,6 +305,10 @@ void SetRuntimeFeaturesFromChromiumFeatures() {
            features::kBrowserVerifiedUserActivationKeyboard, kEnableOnly},
           {wf::EnableBrowserVerifiedUserActivationMouse,
            features::kBrowserVerifiedUserActivationMouse, kEnableOnly},
+#if defined(OS_ANDROID)
+          {wf::EnableWebNfc,
+           features::kWebNfc, kDisableOnly},
+#endif
       };
   for (const auto& mapping : blinkFeatureToBaseFeatureMapping) {
     const bool featureEnabled =

content/public/common/content_features.cc

@@ -832,9 +832,10 @@ const base::Feature kWarmUpNetworkProcess{"WarmUpNetworkProcess",
 const base::Feature kForce60HzRefreshRate{"Force60HzRefreshRate",
                                           base::FEATURE_DISABLED_BY_DEFAULT};
 
-// Controls whether the WebNFC API is enabled:
-// https://w3c.github.io/web-nfc/
-const base::Feature kWebNfc{"WebNFC", base::FEATURE_DISABLED_BY_DEFAULT};
+// Kill switch for the WebNFC feature. This feature can be enabled for all sites
+// using the kEnableExperimentalWebPlatformFeatures flag or by a particular site
+// if it includes an Origin Trial key.  https://w3c.github.io/web-nfc/
+const base::Feature kWebNfc{"WebNFC", base::FEATURE_ENABLED_BY_DEFAULT};
 #endif  // defined(OS_ANDROID)
 
 #if defined(OS_CHROMEOS)