[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..37daf3f2f8147e68c1cc12d0a46edcb36d5987a9
--- /dev/null
+++ b/sync/android/java/src/org/chromium/sync/ModelTypeHelper.java
@@ -0,0 +1,111 @@
+// 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.FieldTrialList;
+import org.chromium.base.VisibleForTesting;
+import org.chromium.base.annotations.JNINamespace;
+import org.chromium.base.library_loader.LibraryLoader;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Helper methods for dealing with ModelTypes.
+ */
+@JNINamespace("syncer")
+public class ModelTypeHelper {
+    private static final String TAG = "ModelTypeHelper";
+
+    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 toString() calls in the isInvalidationType() method.
+    private static Set<String> sNonInvalidationTypes = null;
+    private static Set<String> sNonInvalidationTypesExperiment = null;
+
+    /**
+     * Initializes the non-invalidation sets. Called lazily the first time they're needed.
+     */
+    private static void initNonInvalidationTypes() {

[nyquist, 2015/08/03 20:07:10]

This doesn't seem thread safe. Could you at least add an assert that you are on
the UI thread or something along those lines?

[maxbogue, 2015/08/04 19:43:54]

Decided to make it actually thread safe; PTAL.

+        sNonInvalidationTypes = new HashSet<String>();
+        for (int i = 0; i < NON_INVALIDATION_TYPES_ARRAY.length; i++) {
+            sNonInvalidationTypes.add(toString(NON_INVALIDATION_TYPES_ARRAY[i]));
+        }
+        sNonInvalidationTypesExperiment = new HashSet<String>();
+        sNonInvalidationTypesExperiment.add(toString(ModelType.SESSIONS));
+        sNonInvalidationTypesExperiment.add(toString(ModelType.FAVICON_TRACKING));
+        sNonInvalidationTypesExperiment.add(toString(ModelType.FAVICON_IMAGES));
+    }
+
+    /**
+     * Checks whether a type is allowed to register for invalidations.
+     */
+    private static boolean isInvalidationType(String modelType) {
+        if (sNonInvalidationTypes == null) {

[nyquist, 2015/08/03 20:07:10]

Same about threading here.

[maxbogue, 2015/08/04 19:43:54]

Done.

+            initNonInvalidationTypes();
+        }
+        if (sNonInvalidationTypesExperiment.contains(modelType) && LibraryLoader.isInitialized()) {
+            return !FieldTrialList.findFullName("AndroidSessionNotifications").equals("Disabled");

[Nicolas Zea, 2015/08/04 17:04:53]

To be clear, the experiment being "on" in this case corresponds to the value
"Disabled" right? Everyone else defaults to "Enabled"?

[maxbogue, 2015/08/04 20:06:12]

Yep.

+        }
+        return !sNonInvalidationTypes.contains(modelType);
+    }
+
+    /**
+     * Converts a model type string into an ObjectId.
+     *
+     * If the model type is not an invalidation type, this function uses the string "NULL".
+     */
+    private static ObjectId toObjectId(String modelType) {
+        String objectIdString = isInvalidationType(modelType) ? modelType : "NULL";
+        return ObjectId.newInstance(Types.ObjectSource.CHROME_SYNC, objectIdString.getBytes());
+    }
+
+    @VisibleForTesting
+    public static ObjectId toObjectId(int modelType) {
+        return toObjectId(toString(modelType));
+    }
+
+    /**
+     * Converts a model type to its string representation using JNI.
+     * This is the value that is stored in the invalidation preferences.
+     *
+     * @param modelType the model type to convert to a string.
+     * @return the string representation of the model type constant.
+     */
+    public static String toString(Integer modelType) {

[nyquist, 2015/08/03 20:07:10]

Nit: Could this be 'int'?

[maxbogue, 2015/08/04 19:43:54]

Yes, thanks!

+        // 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} model types to a set of {@link ObjectId}.
+     *
+     * This strips out any {@link ModelType} that is not an invalidation type.
+     */
+    public static Set<ObjectId> modelTypeStringsToObjectIds(Collection<String> modelTypes) {
+        Set<ObjectId> objectIds = new HashSet<ObjectId>();
+        for (String modelType : modelTypes) {
+            if (isInvalidationType(modelType)) {
+                objectIds.add(toObjectId(modelType));
+            }
+        }
+        return objectIds;
+    }
+
+    private static native String nativeModelTypeToNotificationType(int modelType);
+}