Create base.FeatureList to configure test feature values.

This moves ChromeFeatureList.setTestFeatures to a new base.FeatureList
class so it can be shared by other *FeatureList implementations.
Eventually this class will the the primary method of querying Feature
state, but for now it only handles test configuration.

See crrev.com/c/2095445 and the bug for more information.

Bug: 1060097
Change-Id: Idd0c8ebc447f9f936192f81fc1465600f28ad7d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2099470Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750241}

base/BUILD.gn

@@ -3275,6 +3275,7 @@ if (is_android) {
       "android/java/src/org/chromium/base/DiscardableReferencePool.java",
       "android/java/src/org/chromium/base/EarlyTraceEvent.java",
       "android/java/src/org/chromium/base/EventLog.java",
+      "android/java/src/org/chromium/base/FeatureList.java",
       "android/java/src/org/chromium/base/FieldTrialList.java",
       "android/java/src/org/chromium/base/FileUtils.java",
       "android/java/src/org/chromium/base/Function.java",

base/android/java/src/org/chromium/base/FeatureList.java

+// Copyright 2020 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.base;
+
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
+
+import java.util.Map;
+
+/**
+ * Provides shared capabilities for feature flag support.
+ */
+public class FeatureList {
+    /** Map that stores substitution feature flags for tests. */
+    private static @Nullable Map<String, Boolean> sTestFeatures;
+
+    /** Access to default values of the native feature flag. */
+    private static boolean sTestCanUseDefaults;
+
+    private FeatureList() {}
+
+    /**
+     * This is called explicitly for instrumentation tests via Features#applyForInstrumentation().
+     * Unit tests and Robolectric tests must not invoke this and should rely on the {@link Features}
+     * annotations to enable or disable any feature flags.
+     */
+    @VisibleForTesting
+    public static void setTestCanUseDefaultsForTesting() {
+        sTestCanUseDefaults = true;
+    }
+
+    /**
+     * We reset the value to false after the instrumentation test to avoid any unwanted
+     * persistence of the state. This is invoked by Features#reset().
+     */
+    @VisibleForTesting
+    public static void resetTestCanUseDefaultsForTesting() {
+        sTestCanUseDefaults = false;
+    }
+
+    /**
+     * Sets the feature flags to use in JUnit tests, since native calls are not available there.
+     */
+    @VisibleForTesting
+    public static void setTestFeatures(Map<String, Boolean> testFeatures) {
+        sTestFeatures = testFeatures;
+    }
+
+    /**
+     * @return Whether test feature values have been configured.
+     */
+    @VisibleForTesting
+    public static boolean hasTestFeatures() {
+        return sTestFeatures != null;
+    }
+
+    /**
+     * Returns the test value of the feature with the given name.
+     *
+     * @param featureName The name of the feature to query.
+     * @return The test value set for the feature, or null if no test value has been set.
+     * @throws IllegalArgumentException if no test value was set and default values aren't allowed.
+     */
+    @VisibleForTesting
+    public static Boolean getTestValueForFeature(String featureName) {
+        if (hasTestFeatures()) {
+            if (sTestFeatures.containsKey(featureName)) {
+                return sTestFeatures.get(featureName);
+            }
+            if (!sTestCanUseDefaults) {
+                throw new IllegalArgumentException("No test value configured for " + featureName);
+            }
+        }
+        return null;
+    }
+}

chrome/browser/flags/android/java/src/org/chromium/chrome/browser/flags/ChromeFeatureList.java

@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.flags;
 
 import androidx.annotation.VisibleForTesting;
 
+import org.chromium.base.FeatureList;
 import org.chromium.base.annotations.JNINamespace;
 import org.chromium.base.annotations.MainDex;
 import org.chromium.base.annotations.NativeMethods;
@@ -26,44 +27,34 @@ import java.util.Map;
 @JNINamespace("chrome::android")
 @MainDex
 public abstract class ChromeFeatureList {
-    /** Map that stores substitution feature flags for tests. */
-    private static Map<String, Boolean> sTestFeatures;
-
     /** Prevent instantiation. */
     private ChromeFeatureList() {}
 
-    /** Access to default values of the native chrome feature flag. */
-    private static boolean sTestCanUseDefaults;
-
     /**
-     * This is called explicitly for instrumentation tests via Features#applyForInstrumentation().
-     * Unit tests and Robolectric tests must not invoke this and should rely on the {@link Features}
-     * annotations to enable or disable any feature flags.
+     * @see FeatureList#setTestCanUseDefaultsForTesting
      */
+    // TODO(crbug.com/1060097): Migrate callers to the FeatureList equivalent function.
     @VisibleForTesting
     public static void setTestCanUseDefaultsForTesting() {
-        sTestCanUseDefaults = true;
+        FeatureList.setTestCanUseDefaultsForTesting();
     }
 
     /**
-     * We reset the value to false after the instrumentation test to avoid any unwanted
-     * persistence of the state. This is invoked by Features#reset().
+     * @see FeatureList#resetTestCanUseDefaultsForTesting
      */
+    // TODO(crbug.com/1060097): Migrate callers to the FeatureList equivalent function.
     @VisibleForTesting
     public static void resetTestCanUseDefaultsForTesting() {
-        sTestCanUseDefaults = false;
+        FeatureList.resetTestCanUseDefaultsForTesting();
     }
 
     /**
-     * Sets the feature flags to use in JUnit tests, since native calls are not available there.
-     * Do not use directly, prefer using the {@link Features} annotation.
-     *
-     * @see Features
-     * @see Features.Processor
+     * @see FeatureList#setTestFeatures
      */
+    // TODO(crbug.com/1060097): Migrate callers to the FeatureList equivalent function.
     @VisibleForTesting
     public static void setTestFeatures(Map<String, Boolean> features) {
-        sTestFeatures = features;
+        FeatureList.setTestFeatures(features);
     }
 
     /**
@@ -72,7 +63,7 @@ public abstract class ChromeFeatureList {
      *         in tests if test features have been set).
      */
     public static boolean isInitialized() {
-        if (sTestFeatures != null) return true;
+        if (FeatureList.hasTestFeatures()) return true;
         return isNativeInitialized();
     }
 
@@ -120,13 +111,9 @@ public abstract class ChromeFeatureList {
      * @return Whether the feature is enabled or not.
      */
     public static boolean isEnabled(String featureName) {
-        /** FeatureFlags set for testing override the native default value. */
-        if (sTestFeatures != null) {
-            Boolean enabled = sTestFeatures.get(featureName);
-            if (enabled != null) return enabled;
-            if (!sTestCanUseDefaults) throw new IllegalArgumentException(featureName);
-        }
-
+        // FeatureFlags set for testing override the native default value.
+        Boolean testValue = FeatureList.getTestValueForFeature(featureName);
+        if (testValue != null) return testValue;
         return isEnabledInNative(featureName);
     }
 
@@ -142,7 +129,7 @@ public abstract class ChromeFeatureList {
      *   the specified parameter does not exist.
      */
     public static String getFieldTrialParamByFeature(String featureName, String paramName) {
-        if (sTestFeatures != null) return "";
+        if (FeatureList.hasTestFeatures()) return "";
         assert isInitialized();
         return ChromeFeatureListJni.get().getFieldTrialParamByFeature(featureName, paramName);
     }
@@ -161,7 +148,7 @@ public abstract class ChromeFeatureList {
      */
     public static int getFieldTrialParamByFeatureAsInt(
             String featureName, String paramName, int defaultValue) {
-        if (sTestFeatures != null) return defaultValue;
+        if (FeatureList.hasTestFeatures()) return defaultValue;
         assert isInitialized();
         return ChromeFeatureListJni.get().getFieldTrialParamByFeatureAsInt(
                 featureName, paramName, defaultValue);
@@ -181,7 +168,7 @@ public abstract class ChromeFeatureList {
      */
     public static double getFieldTrialParamByFeatureAsDouble(
             String featureName, String paramName, double defaultValue) {
-        if (sTestFeatures != null) return defaultValue;
+        if (FeatureList.hasTestFeatures()) return defaultValue;
         assert isInitialized();
         return ChromeFeatureListJni.get().getFieldTrialParamByFeatureAsDouble(
                 featureName, paramName, defaultValue);
@@ -201,7 +188,7 @@ public abstract class ChromeFeatureList {
      */
     public static boolean getFieldTrialParamByFeatureAsBoolean(
             String featureName, String paramName, boolean defaultValue) {
-        if (sTestFeatures != null) return defaultValue;
+        if (FeatureList.hasTestFeatures()) return defaultValue;
         assert isInitialized();
         return ChromeFeatureListJni.get().getFieldTrialParamByFeatureAsBoolean(
                 featureName, paramName, defaultValue);