Upstream oodles of Chrome for Android code into Chromium.

chrome/android/java_staging/src/org/chromium/chrome/browser/compositor/layouts/OverviewModeBehavior.java

+// 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.chrome.browser.compositor.layouts;
+
+/**
+ * Exposes the current overview mode state as well as a way to listen to overview mode state
+ * changes.
+ */
+public interface OverviewModeBehavior {
+    /**
+     * An observer that is notified when the overview mode state changes.
+     */
+    public interface OverviewModeObserver {
+        /**
+         * Called when overview mode starts showing.
+         * @param showToolbar Whether or not to show the normal toolbar when animating into overview
+         * mode.
+         */
+        void onOverviewModeStartedShowing(boolean showToolbar);
+
+        /**
+         * Called when overview mode finishes showing.
+         */
+        void onOverviewModeFinishedShowing();
+
+        /**
+         * Called when overview mode starts hiding.
+         * @param showToolbar    Whether or not to show the normal toolbar when animating out of
+         *                       overview mode.
+         * @param delayAnimation Whether or not to delay any related overview animations until after
+         *                       overview mode is finished hiding.
+         */
+        void onOverviewModeStartedHiding(boolean showToolbar, boolean delayAnimation);
+
+        /**
+         * Called when overview mode finishes hiding.
+         */
+        void onOverviewModeFinishedHiding();
+    }
+
+    /**
+     * @return Whether or not the overview {@link Layout} is visible.
+     */
+    boolean overviewVisible();
+
+    /**
+     * @param listener Registers {@code listener} for overview mode status changes.
+     */
+    void addOverviewModeObserver(OverviewModeObserver listener);
+
+    /**
+     * @param listener Unregisters {@code listener} for overview mode status changes.
+     */
+    void removeOverviewModeObserver(OverviewModeObserver listener);
+}