AW: support hardcoded flag values in dev UI

This adds support for giving flags a predetermined value. This won't
have any noticeable effect yet because the only flags with values are
finch-related, which are queried either:

- early in startup, before dev UI applis flags
  (https://crbug.com/1059131), or
- in the :webview_service process, which the flag UI doesn't currently
  support (https://crbug.com/1058189)

This does not support applying parameters to base::Features, since this
isn't supported through the basic base::Feature API (it's Finch-specific
functionality).

Bug: 1047493
Test: run_android_webview_junit_tests -f *FlagOverrideHelperTest#*
Change-Id: I773014bea72b4b7156d9e094b431f4fc1e7d0257
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2090882
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747902}

android_webview/java/src/org/chromium/android_webview/common/Flag.java

@@ -5,6 +5,7 @@
 package org.chromium.android_webview.common;
 
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 
 /**
  * Class to represent a commandline flag. This is used by the developer UI to pass flags-to-toggle
@@ -13,29 +14,40 @@ import androidx.annotation.NonNull;
 public class Flag {
     private final String mName;
     private final String mDescription;
+    private final String mEnabledStateValue;
     private final boolean mIsBaseFeature;
 
     /**
      * Creates a Flag which represents a {@code base::Feature}.
      */
     public static Flag baseFeature(@NonNull String name, @NonNull String description) {
-        return new Flag(name, description, true);
+        return new Flag(name, description, /*enabledStateValue=*/null, true);
     }
 
     /**
      * Creates a Flag which represents a commandline switch.
      */
     public static Flag commandLine(@NonNull String name, @NonNull String description) {
-        return new Flag(name, description, false);
+        return new Flag(name, description, /*enabledStateValue=*/null, false);
+    }
+
+    /**
+     * Creates a Flag which represents a commandline switch with a value applied when enabled.
+     */
+    public static Flag commandLine(
+            @NonNull String name, @NonNull String description, @NonNull String enabledStateValue) {
+        return new Flag(name, description, enabledStateValue, false);
     }
 
     /**
      * Calls should use {@link #baseFeature(String, String)} or {@link
      * #commandLine(String, String)} instead.
      */
-    private Flag(@NonNull String name, @NonNull String description, boolean isBaseFeature) {
+    private Flag(@NonNull String name, @NonNull String description,
+            @Nullable String enabledStateValue, boolean isBaseFeature) {
         mName = name;
         mDescription = description;
+        mEnabledStateValue = enabledStateValue;
         mIsBaseFeature = isBaseFeature;
     }
 
@@ -49,6 +61,15 @@ public class Flag {
         return mDescription;
     }
 
+    /**
+     * Fetch the value to apply to the flag when enabled, or {@code null} if the flag doesn't take a
+     * value.
+     */
+    @Nullable
+    public String getEnabledStateValue() {
+        return mEnabledStateValue;
+    }
+
     /**
      * Indicates whether this is a {@code base::Feature} or a commandline flag.
      *

android_webview/java/src/org/chromium/android_webview/common/FlagOverrideHelper.java

@@ -73,7 +73,10 @@ public class FlagOverrideHelper {
                     disabledFeatures.add(flag.getName());
                 }
             } else {
-                if (enabled) {
+                if (enabled && flag.getEnabledStateValue() != null) {
+                    CommandLine.getInstance().appendSwitchWithValue(
+                            flag.getName(), flag.getEnabledStateValue());
+                } else if (enabled) {
                     CommandLine.getInstance().appendSwitch(flag.getName());
                 } else {
                     CommandLine.getInstance().removeSwitch(flag.getName());

android_webview/java/src/org/chromium/android_webview/common/ProductionSupportedFlagList.java

@@ -30,15 +30,16 @@ public final class ProductionSupportedFlagList {
             Flag.commandLine("show-composited-layer-borders",
                     "Renders a border around compositor layers to help debug and study layer "
                             + "compositing."),
-            Flag.commandLine(AwSwitches.FINCH_SEED_EXPIRATION_AGE + "=0",
-                    "Forces all variations seeds to be considered stale."),
+            Flag.commandLine(AwSwitches.FINCH_SEED_EXPIRATION_AGE,
+                    "Forces all variations seeds to be considered stale.", "0"),
             Flag.commandLine(AwSwitches.FINCH_SEED_IGNORE_PENDING_DOWNLOAD,
                     "Forces the WebView service to reschedule a variations seed download job even "
                             + "if one is already pending."),
-            Flag.commandLine(AwSwitches.FINCH_SEED_MIN_DOWNLOAD_PERIOD + "=0",
-                    "Disables throttling of variations seed download jobs."),
-            Flag.commandLine(AwSwitches.FINCH_SEED_MIN_UPDATE_PERIOD + "=0",
-                    "Disables throttling of new variations seed requests to the WebView service."),
+            Flag.commandLine(AwSwitches.FINCH_SEED_MIN_DOWNLOAD_PERIOD,
+                    "Disables throttling of variations seed download jobs.", "0"),
+            Flag.commandLine(AwSwitches.FINCH_SEED_MIN_UPDATE_PERIOD,
+                    "Disables throttling of new variations seed requests to the WebView service.",
+                    "0"),
             Flag.commandLine("webview-log-js-console-messages",
                     "Mirrors JavaScript console messages to system logs."),
             Flag.commandLine(AwSwitches.CRASH_UPLOADS_ENABLED_FOR_TESTING_SWITCH,

android_webview/junit/src/org/chromium/android_webview/robolectric/common/FlagOverrideHelperTest.java

@@ -39,6 +39,7 @@ public class FlagOverrideHelperTest {
     private static final Flag[] sMockFlagList = {
             Flag.commandLine("flag-1", "This is flag 1"),
             Flag.commandLine("flag-2", "This is flag 2"),
+            Flag.commandLine("flag-3", "This is flag 3", "some-value"),
             Flag.baseFeature("feature-1", "This is feature 1"),
             Flag.baseFeature("feature-2", "This is feature 2"),
     };
@@ -105,6 +106,30 @@ public class FlagOverrideHelperTest {
                 CommandLine.getInstance().hasSwitch("flag-1"));
     }
 
+    @Test
+    @SmallTest
+    public void testAddFlag_noValue() {
+        Map<String, Boolean> map = new HashMap<>();
+        map.put("flag-1", true);
+        FlagOverrideHelper helper = new FlagOverrideHelper(sMockFlagList);
+        helper.applyFlagOverrides(map);
+        Assert.assertTrue("The 'flag-1' commandline flag should be applied",
+                CommandLine.getInstance().hasSwitch("flag-1"));
+        Assert.assertNull("The 'flag-1' commandline flag should not have a value",
+                CommandLine.getInstance().getSwitchValue("flag-1"));
+    }
+
+    @Test
+    @SmallTest
+    public void testAddFlag_withValue() {
+        Map<String, Boolean> map = new HashMap<>();
+        map.put("flag-3", true);
+        FlagOverrideHelper helper = new FlagOverrideHelper(sMockFlagList);
+        helper.applyFlagOverrides(map);
+        Assert.assertEquals("The 'flag-3' commandline flag should have a value", "some-value",
+                CommandLine.getInstance().getSwitchValue("flag-3"));
+    }
+
     @Test
     @SmallTest
     public void testRemoveFlag_notYetAdded() {

android_webview/nonembedded/java/src/org/chromium/android_webview/devui/FlagsActivity.java

@@ -162,7 +162,11 @@ public class FlagsActivity extends Activity {
             Spinner flagToggle = view.findViewById(R.id.flag_toggle);
 
             Flag flag = getItem(position);
-            flagName.setText(flag.getName());
+            String label = flag.getName();
+            if (flag.getEnabledStateValue() != null) {
+                label += "=" + flag.getEnabledStateValue();
+            }
+            flagName.setText(label);
             flagDescription.setText(flag.getDescription());
             ArrayAdapter<String> adapter =
                     new ArrayAdapter<>(FlagsActivity.this, R.layout.flag_states, sFlagStates);