Automatically list Finch parameters to cache

Bug: 1067145
Change-Id: I25d2b9b8537ea665767f90658702a3316a6ff58d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2134572
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#761326}

chrome/android/java/src/org/chromium/chrome/browser/app/flags/ChromeCachedFlags.java

@@ -4,6 +4,9 @@
 
 package org.chromium.chrome.browser.app.flags;
 
+import android.text.TextUtils;
+
+import org.chromium.base.annotations.RemovableInRelease;
 import org.chromium.chrome.browser.compositor.layouts.content.TabContentManager;
 import org.chromium.chrome.browser.firstrun.FirstRunUtils;
 import org.chromium.chrome.browser.flags.CachedFeatureFlags;
@@ -16,6 +19,7 @@ import org.chromium.chrome.browser.tasks.tab_management.TabUiFeatureUtilities;
 import org.chromium.chrome.browser.toolbar.bottom.BottomToolbarVariationManager;
 import org.chromium.chrome.features.start_surface.StartSurfaceConfiguration;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 
@@ -84,6 +88,7 @@ public class ChromeCachedFlags {
                 TabUiFeatureUtilities.TAB_GRID_LAYOUT_ANDROID_NEW_TAB_TILE,
                 TabUiFeatureUtilities.THUMBNAIL_ASPECT_RATIO);
         // clang-format on
+        tryToCatchMissingParameters(fieldTrialsToCache);
         CachedFeatureFlags.cacheFieldTrialParameters(fieldTrialsToCache);
 
         // TODO(crbug.com/1062013): Remove this after M85.
@@ -98,6 +103,22 @@ public class ChromeCachedFlags {
         mIsFinishedCachingNativeFlags = true;
     }
 
+    @RemovableInRelease
+    private void tryToCatchMissingParameters(List<CachedFieldTrialParameter> listed) {
+        // All instances of CachedFieldTrialParameter should be manually passed to
+        // CachedFeatureFlags.cacheFieldTrialParameters(). The following checking is a best-effort
+        // attempt to try to catch accidental omissions. It cannot replace the list because some
+        // instances might not be instantiated if the classes they belong to are not accessed yet.
+        List<String> omissions = new ArrayList<>();
+        for (CachedFieldTrialParameter trial : CachedFieldTrialParameter.getAllInstances()) {
+            if (listed.contains(trial)) continue;
+            omissions.add(trial.getFeatureName() + ":" + trial.getParameterName());
+        }
+        assert omissions.isEmpty()
+            : "The following trials are not correctly cached: "
+                + TextUtils.join(", ", omissions);
+    }
+
     /**
      * Caches flags that are enabled in ServiceManager only mode and must take effect on startup but
      * are set via native code. This function needs to be called in ServiceManager only mode to mark

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

@@ -7,10 +7,14 @@ package org.chromium.chrome.browser.flags;
 import androidx.annotation.IntDef;
 import androidx.annotation.VisibleForTesting;
 
+import org.chromium.base.annotations.CheckDiscard;
+import org.chromium.base.annotations.RemovableInRelease;
 import org.chromium.chrome.browser.preferences.ChromePreferenceKeys;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import java.util.HashSet;
+import java.util.Set;
 
 /**
  * A field trial parameter in the variations framework that is cached by {@link CachedFeatureFlags}.
@@ -29,6 +33,9 @@ public abstract class CachedFieldTrialParameter {
         int DOUBLE = 3;
     }
 
+    @CheckDiscard("crbug.com/1067145")
+    private static Set<CachedFieldTrialParameter> sAllInstances;
+
     private final String mFeatureName;
     private final String mParameterName;
     private final @FieldTrialParameterType int mType;
@@ -40,6 +47,21 @@ public abstract class CachedFieldTrialParameter {
         mParameterName = parameterName;
         mType = type;
         mPreferenceKeyOverride = preferenceKeyOverride;
+
+        registerInstance();
+    }
+
+    @RemovableInRelease
+    private void registerInstance() {
+        if (sAllInstances == null) {
+            sAllInstances = new HashSet<>();
+        }
+        sAllInstances.add(this);
+    }
+
+    @CheckDiscard("crbug.com/1067145")
+    public static Set<CachedFieldTrialParameter> getAllInstances() {
+        return sAllInstances;
     }
 
     /**