Integrate WebUSB with Feature Policy

third_party/WebKit/Source/platform/feature_policy/FeaturePolicy.cpp

Index: third_party/WebKit/Source/platform/feature_policy/FeaturePolicy.cpp
diff --git a/third_party/WebKit/Source/platform/feature_policy/FeaturePolicy.cpp b/third_party/WebKit/Source/platform/feature_policy/FeaturePolicy.cpp
index f89c965b35075a0057e00fe885d3e977f2c26074..0c8e2a45b7dfcacb25d82172279d177c358eab80 100644
--- a/third_party/WebKit/Source/platform/feature_policy/FeaturePolicy.cpp
+++ b/third_party/WebKit/Source/platform/feature_policy/FeaturePolicy.cpp
@@ -134,6 +134,7 @@ const FeatureNameMap& GetDefaultFeatureNameMap() {
     default_feature_name_map.Set("fullscreen",
                                  WebFeaturePolicyFeature::kFullscreen);
     default_feature_name_map.Set("payment", WebFeaturePolicyFeature::kPayment);
+    default_feature_name_map.Set("usb", WebFeaturePolicyFeature::kUsb);

[iclelland.google, 2017/05/02 14:42:52]

Can you make this line conditional on RuntimeEnabledFeatures::WebUSB? WebUSB
implies FP, but not the other way around, and we shouldn't be recognizing the
feature in policy declarations if WebUSB is disabled in the browser.

[Reilly Grant (use Gerrit), 2017/05/02 19:29:05]

WebUSB is an Origin Trial so RuntimeEnabledFeature::webUSBEnabled() may return
false even if the API is exposed to the web. It's confusing but that's what
we're stuck with.

[iclelland, 2017/05/04 15:24:08]

Right, of course. (And other than plumbing the execution context down to this
method, that's probably not going to change soon.) I was thinking that this was
part of shipping WebUSB, and removing it from origin trials.

     if (RuntimeEnabledFeatures::featurePolicyExperimentalFeaturesEnabled()) {
       default_feature_name_map.Set("vibrate",
                                    WebFeaturePolicyFeature::kVibrate);