Move 'wake-lock' feature policy feature behind runtime flag

This ensures that the 'wake-lock' feature is not parsed in feature
policy directives unless the WakeLock runtime flag is enabled.

Bug: 925454
Change-Id: Ic8043be2f499295f4246d99866180c2aab222ad7
Reviewed-on: https://chromium-review.googlesource.com/c/1436201Reviewed-by: Rick Byers <rbyers@chromium.org>
Commit-Queue: Ian Clelland <iclelland@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626229}

third_party/blink/renderer/core/feature_policy/feature_policy.cc

@@ -256,8 +256,6 @@ const FeatureNameMap& GetDefaultFeatureNameMap() {
     ASSERT_ORIGIN_TRIAL(WebVR);
     ASSERT_ORIGIN_TRIAL(WebXR);
     default_feature_name_map.Set("vr", mojom::FeaturePolicyFeature::kWebVr);
-    default_feature_name_map.Set("wake-lock",
-                                 mojom::FeaturePolicyFeature::kWakeLock);
     if (RuntimeEnabledFeatures::ExperimentalProductivityFeaturesEnabled()) {
       default_feature_name_map.Set(
           "layout-animations", mojom::FeaturePolicyFeature::kLayoutAnimations);
@@ -303,6 +301,10 @@ const FeatureNameMap& GetDefaultFeatureNameMap() {
       default_feature_name_map.Set("magnetometer",
                                    mojom::FeaturePolicyFeature::kMagnetometer);
     }
+    if (RuntimeEnabledFeatures::WakeLockEnabled()) {
+      default_feature_name_map.Set("wake-lock",
+                                   mojom::FeaturePolicyFeature::kWakeLock);
+    }
     if (RuntimeEnabledFeatures::WebUSBEnabled()) {
       default_feature_name_map.Set("usb", mojom::FeaturePolicyFeature::kUsb);
     }

third_party/blink/web_tests/virtual/stable/webexposed/feature-policy-features-expected.txt

@@ -18,5 +18,4 @@ speaker
 sync-xhr
 usb
 vr
-wake-lock