Use feature architecture as kill switch for WebAPKs instead of field trial

chrome/browser/android/chrome_feature_list.cc

Index: chrome/browser/android/chrome_feature_list.cc
diff --git a/chrome/browser/android/chrome_feature_list.cc b/chrome/browser/android/chrome_feature_list.cc
index 0f9705fff70df981df9e574da2e46e6981fdf8a7..43c932be459aa50f621294e9ca05946a22b91314 100644
--- a/chrome/browser/android/chrome_feature_list.cc
+++ b/chrome/browser/android/chrome_feature_list.cc
@@ -51,6 +51,7 @@ const base::Feature* kFeaturesExposedToJava[] = {
     &kSpecialLocaleFeature,
     &kSpecialLocaleWrapper,
     &kTabReparenting,
+    &kWebApk,
     &kCCTExternalLinkHandling,
     &offline_pages::kOfflinePagesBackgroundLoadingFeature,
     &offline_pages::kBackgroundLoaderForDownloadsFeature,
@@ -103,6 +104,12 @@ const base::Feature kCCTExternalLinkHandling{"CCTExternalLinkHandling",
 const base::Feature kUserMediaScreenCapturing{
     "UserMediaScreenCapturing", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Makes "Add to Home screen" in the app menu generate an APK for the shortcut
+// URL which opens Chrome in fullscreen.
+// For WebAPKs to be enabled, the WebAPK feature must be enabled and the

[dominickn, 2016/10/24 04:04:17]

Is it strictly necessary for the feature to be enabled and --enable-webapk to be
specified as well?

I believe you should be able to make the --enable-webapk flag enable this
feature, so you can probably remove the final two lines of this comment. 
Disabled features should take precedence over enabled features, so if you
kill-switch WebAPKs via Finch the disable should win even if the flag is on.

+// --enable-webapk command line flag must be set.
+const base::Feature kWebApk{"WebAPK", base::FEATURE_ENABLED_BY_DEFAULT};
+
 static jboolean IsEnabled(JNIEnv* env,
                           const JavaParamRef<jclass>& clazz,
                           const JavaParamRef<jstring>& jfeature_name) {