[Android History] Add Android history manager UI and bridge

chrome/android/java/src/org/chromium/chrome/browser/history/HistoryManagerUtils.java

+// 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.chrome.browser.history;
+
+import android.app.Activity;
+import android.content.Intent;
+import android.text.TextUtils;
+
+import org.chromium.base.CommandLine;
+import org.chromium.chrome.browser.IntentHandler;
+import org.chromium.components.variations.VariationsAssociatedData;
+
+/**
+ * Utility methods for the browsing history manager.
+ */
+public class HistoryManagerUtils {
+    private static final String FIELD_TRIAL_NAME = "AndroidHistoryManager";
+    private static final String ENABLE_HISTORY_SWTICH = "enable_android_history_manager";
+    private static Boolean sNativeHistoryEnabled;
+
+    /**
+    * @return Whether the Android-specific browsing history manager is enabled.
+    */
+    public static boolean isAndroidHistoryManagerEnabled() {

[gone, 2016/12/02 19:34:37]

Does this need to worry about what thread it's called on (i.e. do we need to
synchronize on something)?

[Theresa, 2016/12/02 20:49:33]

It's currently only called from the UI thread but tests may change that. Moved
most of this method into a synchronized block.

+        if (sNativeHistoryEnabled == null) {
+            if (CommandLine.getInstance().hasSwitch(ENABLE_HISTORY_SWTICH)) {
+                sNativeHistoryEnabled = true;
+            } else {
+                sNativeHistoryEnabled = TextUtils.equals("true",
+                        VariationsAssociatedData.getVariationParamValue(FIELD_TRIAL_NAME,
+                                ENABLE_HISTORY_SWTICH));
+            }
+        }
+
+        return sNativeHistoryEnabled;
+    }
+
+    /**
+    * @return Whether the Android-specific browsing history UI is was shown.
+    */
+    public static boolean showHistoryManager(Activity activity) {
+        if (!isAndroidHistoryManagerEnabled()) return false;
+
+        // TODO(twellington): Add support for tablets
+        Intent intent = new Intent();
+        intent.setClass(activity.getApplicationContext(), HistoryActivity.class);
+        intent.putExtra(IntentHandler.EXTRA_PARENT_COMPONENT, activity.getComponentName());
+        activity.startActivity(intent);
+
+        return true;
+    }
+}