Add fake for InstanceIDWithSubtype.java, in order to re-use unit test

components/gcm_driver/instance_id/android/javatests/src/org/chromium/components/gcm_driver/instance_id/FakeInstanceIDWithSubtype.java

Index: components/gcm_driver/instance_id/android/javatests/src/org/chromium/components/gcm_driver/instance_id/FakeInstanceIDWithSubtype.java
diff --git a/components/gcm_driver/instance_id/android/javatests/src/org/chromium/components/gcm_driver/instance_id/FakeInstanceIDWithSubtype.java b/components/gcm_driver/instance_id/android/javatests/src/org/chromium/components/gcm_driver/instance_id/FakeInstanceIDWithSubtype.java
new file mode 100644
index 0000000000000000000000000000000000000000..ebdba3c9af5dc8630475baa95a73ceab7c4b0ae1
--- /dev/null
+++ b/components/gcm_driver/instance_id/android/javatests/src/org/chromium/components/gcm_driver/instance_id/FakeInstanceIDWithSubtype.java
@@ -0,0 +1,133 @@
+// Copyright 2016 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.components.gcm_driver.instance_id;
+
+import android.content.Context;
+import android.os.Bundle;
+import android.os.Looper;
+
+import com.google.android.gms.iid.InstanceID;
+
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+
+import java.io.IOException;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Random;
+
+/**
+ * Fake for InstanceIDWithSubtype. Doesn't hit the network or filesystem (so instance IDs don't
+ * survive restarts, and sending messages to tokens via the GCM server won't work).
+ */
+@JNINamespace("instance_id")
+public class FakeInstanceIDWithSubtype extends InstanceIDWithSubtype {
+    private String mId = null;
+    private long mCreationTime = 0;
+    private Map<String, String> mTokens = new HashMap<>();
+
+    /**
+     * Enable this in all InstanceID tests to use this fake instead of hitting the network/disk.
+     * @return The previous value.
+     */
+    @CalledByNative
+    public static boolean clearDataAndSetEnabled(boolean enable) {
+        synchronized (InstanceID.class) {
+            sSubtypeInstances.clear();
+            boolean wasEnabled = sFakeFactoryForTesting != null;
+            if (enable) {
+                sFakeFactoryForTesting = new FakeFactory() {
+                    @Override
+                    public InstanceIDWithSubtype create(Context context, String subtype) {
+                        return new FakeInstanceIDWithSubtype(context, subtype);
+                    }
+                };
+            } else {
+                sFakeFactoryForTesting = null;
+            }
+            return wasEnabled;
+        }
+    }
+
+    private FakeInstanceIDWithSubtype(Context context, String subtype) {
+        super(context, subtype);
+    }
+
+    @Override
+    public String getId() {
+        if (mId == null) {
+            mCreationTime = System.currentTimeMillis();
+            mId = randomBase64(11 /* length */);
+        }
+        return mId;
+    }
+
+    @Override
+    public long getCreationTime() {
+        return mCreationTime;
+    }
+
+    @Override
+    public String getToken(String authorizedEntity, String scope) throws IOException {
+        return getToken(authorizedEntity, scope, null);
+    }
+
+    @Override
+    public String getToken(String authorizedEntity, String scope, Bundle extras)
+            throws IOException {
+        if (Looper.getMainLooper() == Looper.myLooper()) {
+            throw new IOException(InstanceID.ERROR_MAIN_THREAD);
+        }
+        String key = getSubtype() + ',' + authorizedEntity + ',' + scope;
+        String token = mTokens.get(key);
+        if (token == null) {
+            getId();
+            token = mId + ':' + randomBase64(140 /* length */);
+            mTokens.put(key, token);
+        }
+        return token;
+    }
+
+    @Override
+    public void deleteToken(String authorizedEntity, String scope) throws IOException {
+        if (Looper.getMainLooper() == Looper.myLooper()) {
+            throw new IOException(InstanceID.ERROR_MAIN_THREAD);
+        }
+        String key = getSubtype() + ',' + authorizedEntity + ',' + scope;
+        mTokens.remove(key);
+        // Calling deleteToken causes ID to be generated; can be observed though getCreationTime.
+        getId();
+    }
+
+    @Override
+    public void deleteInstanceID() throws IOException {
+        synchronized (InstanceID.class) {
+            sSubtypeInstances.remove(getSubtype());
+            if (Looper.getMainLooper() == Looper.myLooper()) {
+                throw new IOException(InstanceID.ERROR_MAIN_THREAD);
+            }
+            mTokens.clear();
+            mCreationTime = 0;
+            mId = null;
+        }
+    }
+
+    /** Returns a random base64url encoded string. */
+    private static String randomBase64(int encodedLength) {
+        // It would probably make more sense for this method to produce fixed-length plaintext,
+        // rather than fixed-length encodings that correspond to variable-length plaintext.
+        // But the added randomness helps avoid us depending on the length of tokens GCM gives us.
+        final String base64urlAlphabet =
+                "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_";
+        Random random = new Random();
+        StringBuilder sb = new StringBuilder(encodedLength);
+        for (int i = 0; i < encodedLength; i++) {
+            int index = random.nextInt(base64urlAlphabet.length());
+            sb.append(base64urlAlphabet.charAt(index));
+        }
+        return sb.toString();
+    }
+}