Read feature param for Physical Web experiment

chrome/android/java/src/org/chromium/chrome/browser/physicalweb/PhysicalWeb.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.physicalweb;
 
 import android.content.Context;
 import android.os.AsyncTask;
 
 import org.chromium.base.CommandLine;
 import org.chromium.chrome.browser.ChromeApplication;
 import org.chromium.chrome.browser.ChromeSwitches;
 import org.chromium.chrome.browser.ChromeVersionInfo;
 
 /**
  * This class provides the basic interface to the Physical Web feature.
  */
 public class PhysicalWeb {
+    private static final String FIELD_TRIAL_NAME = "PhysicalWeb";
+    private static final String ENABLED_PARAM = "enabled";
+    private static final String ENABLED_VALUE = "true";
+
     /**
      * Evaluate whether the environment is one in which the Physical Web should
      * be enabled.
      * @return true if the PhysicalWeb should be enabled
      */
     public static boolean featureIsEnabled() {
+        // TODO(cco3): Remove chrome://flag after Finch is experiment is more in place.

[mmocny, 2015/12/10 15:07:04]

I thought we still want to make the chrome://flag available to allow explicit
opt-in?

[cco3, 2015/12/11 21:32:19]

That's what I thought too, but this seriously complicates things because it's
not clear whether the flag was turned off intentionally as a hard signal that
the feature is to be turned off.  Matt might be able to comment further since
he's been working with this logic.

People can still turn it on with a command line flag though.

         boolean allowedChannel =
                 ChromeVersionInfo.isLocalBuild() || ChromeVersionInfo.isDevBuild();
         boolean switchEnabled =
                 CommandLine.getInstance().hasSwitch(ChromeSwitches.ENABLE_PHYSICAL_WEB);
-        return allowedChannel && switchEnabled;
+        // Check chrome://flag, command line flag, and finch, in that order
+        return (allowedChannel && switchEnabled) || getBooleanParam(ENABLED_PARAM);
     }
 
     /**
      * Start the Physical Web feature.
      * At the moment, this only enables URL discovery over BLE.
      * @param application An instance of {@link ChromeApplication}, used to get the
      * appropriate PhysicalWebBleClient implementation.
      */
     public static void startPhysicalWeb(ChromeApplication application) {
         PhysicalWebBleClient physicalWebBleClient = PhysicalWebBleClient.getInstance(application);
@@ skipping 23 matching lines @@
 
     private static void clearUrlsAsync(final Context context) {
         Runnable task = new Runnable() {
             @Override
             public void run() {
                 UrlManager.getInstance(context).clearUrls();
             }
         };
         AsyncTask.THREAD_POOL_EXECUTOR.execute(task);
     }
+
+    /**
+     * Gets a boolean Finch parameter, assuming the <paramName>="true" format.  Also checks for a
+     * command-line switch with the same name, for easy local testing.
+     * @param paramName The name of the Finch parameter (or command-line switch) to get a value for.
+     * @param defaultValue The default value to return when there's no param or switch.
+     * @return Whether the Finch param is defined with a value "true", if there's a command-line
+     *         flag present with any value.
+     */
+    private static boolean getBooleanParam(String paramName, boolean defaultValue) {

[nyquist, 2015/12/10 00:04:06]

defaultValue doesn't seem to be used? In the call above you don't seem to be
passing it either. Did you try compiling this?

[cco3, 2015/12/10 01:22:54]

Done.

+        if (CommandLine.getInstance().hasSwitch(paramName)) {
+            return true;
+        }
+        return TextUtils.equals(ENABLED_VALUE,
+                VariationsAssociatedData.getVariationParamValue(FIELD_TRIAL_NAME, paramName));
+    }
 }