[Sync] Add auto-generated ModelType in Java.

sync/android/java/src/org/chromium/sync/ModelTypeHelper.java

Index: sync/android/java/src/org/chromium/sync/ModelTypeHelper.java
diff --git a/sync/android/java/src/org/chromium/sync/ModelTypeHelper.java b/sync/android/java/src/org/chromium/sync/ModelTypeHelper.java
new file mode 100644
index 0000000000000000000000000000000000000000..3e053c296a10a3e9ceafdd979f1fa2fb8494dfcb
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+++ b/sync/android/java/src/org/chromium/sync/ModelTypeHelper.java
@@ -0,0 +1,114 @@
+// 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.sync;
+
+import com.google.ipc.invalidation.external.client.types.ObjectId;
+import com.google.protos.ipc.invalidation.Types;
+
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.JNINamespace;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Helper methods for dealing with ModelTypes.
+ *
+ * This class deals primarily with converting ModelTypes into notification types (string
+ * representations that are used to register for invalidations) and converting notification
+ * types into the actual ObjectIds used for invalidations.
+ *
+ */
+@JNINamespace("syncer")
+public class ModelTypeHelper {
+    private static final String TAG = "ModelTypeHelper";
+
+    private static final Object sLock = new Object();
+
+    private static final int[] NON_INVALIDATION_TYPES_ARRAY = new int[] {
+        ModelType.PROXY_TABS
+    };
+
+    // Convenience sets for checking whether a type can have invalidations. Some ModelTypes
+    // such as PROXY_TABS are not real types and can't be registered. Initializing these
+    // once reduces toNotificationType() calls in the isInvalidationType() method.
+    private static Set<String> sNonInvalidationTypes = null;
+
+    /**
+     * Initializes the non-invalidation sets. Called lazily the first time they're needed.
+     */
+    private static void initNonInvalidationTypes() {
+        synchronized (sLock) {
+            if (sNonInvalidationTypes != null) return;
+
+            sNonInvalidationTypes = new HashSet<String>();
+            for (int i = 0; i < NON_INVALIDATION_TYPES_ARRAY.length; i++) {
+                sNonInvalidationTypes.add(toNotificationType(NON_INVALIDATION_TYPES_ARRAY[i]));
+            }
+        }
+    }
+
+    /**
+     * Checks whether a type is allowed to register for invalidations.
+     */
+    private static boolean isInvalidationType(String notificationType) {
+        initNonInvalidationTypes();
+        return !sNonInvalidationTypes.contains(notificationType);
+    }
+
+    /**
+     * Converts a notification type into an ObjectId.
+     *
+     * If the model type is not an invalidation type, this function uses the string "NULL".
+     */
+    private static ObjectId toObjectId(String notificationType) {
+        String objectIdString = isInvalidationType(notificationType) ? notificationType : "NULL";
+        return ObjectId.newInstance(Types.ObjectSource.CHROME_SYNC, objectIdString.getBytes());
+    }
+
+    @VisibleForTesting
+    public static ObjectId toObjectId(int modelType) {
+        return toObjectId(toNotificationType(modelType));
+    }
+
+    /**
+     * Converts a model type to its notification type representation using JNI.
+     *
+     * This is the value that is stored in the invalidation preferences and used to
+     * register for invalidations.
+     *
+     * @param modelType the model type to convert to a string.
+     * @return the string representation of the model type constant.
+     */
+    public static String toNotificationType(int modelType) {
+        // Because PROXY_TABS isn't an invalidation type, it doesn't have a string from native,
+        // but for backwards compatibility we need to keep its pref value the same as the old
+        // ModelType enum name value.
+        if (modelType == ModelType.PROXY_TABS) {
+            return "PROXY_TABS";
+        }
+        return nativeModelTypeToNotificationType(modelType);
+    }
+
+    /**
+     * Converts a set of {@link String} notification types to a set of {@link ObjectId}.
+     *
+     * This function assumes that all the strings passed in were generated with
+     * ModelTypeHelper.toNotificationType. Any notification types that are nonInvalidationTypes
+     * are filtered out.
+     */
+    public static Set<ObjectId> notificationTypesToObjectIds(Collection<String> notificationTypes) {
+        Set<ObjectId> objectIds = new HashSet<ObjectId>();
+        for (String notificationType : notificationTypes) {
+            if (isInvalidationType(notificationType)) {
+                objectIds.add(toObjectId(notificationType));
+            }
+        }
+        return objectIds;
+    }
+
+    private static native String nativeModelTypeToNotificationType(int modelType);
+}