[Touchless] Add "Remove" context menu item for last tab button

Selecting remove will remove last navigation from history and switch
last button to Google logo.
The logic is implemented by remembering timestamp of last removed
history entry in SharedPreferences. Only History items with later
timestamp are displayed on last tab button.

BUG=959317
R=wylieb@chromium.org

Change-Id: I8e67afca631bbc233d90f34791eff146bc1f37dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1644155Reviewed-by: Brandon Wylie <wylieb@chromium.org>
Commit-Queue: Pavel Yatsuk <pavely@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666044}

chrome/android/touchless/java/src/org/chromium/chrome/browser/touchless/OpenLastTabMediator.java

@@ -41,6 +41,8 @@ import java.util.List;
 class OpenLastTabMediator extends EmptyTabObserver
         implements HistoryProvider.BrowsingHistoryObserver, FocusableComponent {
     private static final String FIRST_LAUNCHED_KEY = "TOUCHLESS_WAS_FIRST_LAUNCHED";
+    private static final String LAST_REMOVED_VISIT_TIMESTAMP_KEY =
+            "TOUCHLESS_LAST_REMOVED_VISIT_TIMESTAMP";
 
     private final Context mContext;
     private final Profile mProfile;
@@ -52,6 +54,10 @@ class OpenLastTabMediator extends EmptyTabObserver
     private final RoundedIconGenerator mIconGenerator;
     private final LargeIconBridge mIconBridge;
 
+    private HistoryItem mHistoryItem;
+    private boolean mPreferencesRead;
+    private long mLastRemovedVisitTimestamp = Long.MIN_VALUE;
+
     OpenLastTabMediator(Context context, Profile profile, NativePageHost nativePageHost,
             PropertyModel model, OpenLastTabView view) {
         mModel = model;
@@ -67,20 +73,31 @@ class OpenLastTabMediator extends EmptyTabObserver
                 ViewUtils.createDefaultRoundedIconGenerator(mContext.getResources(), false);
         mIconBridge = new LargeIconBridge(mProfile);
 
+        readPreferences();
+
+        // TODO(wylieb):Investigate adding an item limit to the API.
+        // Query the history for everything (no API exists to only query for the most recent).
+        refreshHistoryData();
+    }
+
+    private SharedPreferences getSharedPreferences() {
+        return mNativePageHost.getActiveTab().getActivity().getPreferences(Context.MODE_PRIVATE);
+    }
+
+    private void readPreferences() {
         PostTask.postTask(TaskTraits.USER_VISIBLE, () -> {
             // Check if this is a first launch of Chrome.
-            SharedPreferences prefs = mNativePageHost.getActiveTab().getActivity().getPreferences(
-                    Context.MODE_PRIVATE);
+            SharedPreferences prefs = getSharedPreferences();
             boolean firstLaunched = prefs.getBoolean(FIRST_LAUNCHED_KEY, true);
             prefs.edit().putBoolean(FIRST_LAUNCHED_KEY, false).apply();
+            mLastRemovedVisitTimestamp =
+                    prefs.getLong(LAST_REMOVED_VISIT_TIMESTAMP_KEY, Long.MIN_VALUE);
             PostTask.postTask(UiThreadTaskTraits.USER_VISIBLE, () -> {
+                mPreferencesRead = true;
                 mModel.set(OpenLastTabProperties.OPEN_LAST_TAB_FIRST_LAUNCH, firstLaunched);
+                updateModel();
             });
         });
-
-        // TODO(wylieb):Investigate adding an item limit to the API.
-        // Query the history for everything (no API exists to only query for the most recent).
-        refreshHistoryData();
     }
 
     void destroy() {
@@ -115,41 +132,55 @@ class OpenLastTabMediator extends EmptyTabObserver
     @Override
     public void onQueryHistoryComplete(List<HistoryItem> items, boolean hasMorePotentialMatches) {
         if (items.size() == 0) {
+            mHistoryItem = null;
+        } else {
+            // First item is most recent.
+            mHistoryItem = items.get(0);
+        }
+        if (mPreferencesRead) {
+            updateModel();
+        }
+    }
+
+    // updateModel is only called after preferences are read. It populates model with data from
+    // mHistoryItem.
+    private void updateModel() {
+        if (mHistoryItem == null || mHistoryItem.getTimestamp() <= mLastRemovedVisitTimestamp) {
             // Consider the case where the history has nothing in it to be a failure.
             mModel.set(OpenLastTabProperties.OPEN_LAST_TAB_LOAD_SUCCESS, false);
             return;
         }
 
-        // First item is most recent.
-        HistoryItem item = items.get(0);
-
-        String title = UrlUtilities.getDomainAndRegistry(item.getUrl(), false);
+        String title = UrlUtilities.getDomainAndRegistry(mHistoryItem.getUrl(), false);
         // Default the timestamp to happening just now. If it happened over a minute ago, calculate
         // and set the relative timestamp string.
         String timestamp = mContext.getResources().getString(R.string.open_last_tab_just_now);
         long now = System.currentTimeMillis();
-        if (now - item.getTimestamp() > MINUTE_IN_MILLIS) {
-            timestamp = getRelativeTimeSpanString(item.getTimestamp(), now, MINUTE_IN_MILLIS)
-                                .toString();
+        if (now - mHistoryItem.getTimestamp() > MINUTE_IN_MILLIS) {
+            timestamp =
+                    getRelativeTimeSpanString(mHistoryItem.getTimestamp(), now, MINUTE_IN_MILLIS)
+                            .toString();
         }
 
         mModel.set(OpenLastTabProperties.OPEN_LAST_TAB_TITLE, title);
         mModel.set(OpenLastTabProperties.OPEN_LAST_TAB_TIMESTAMP, timestamp);
-        boolean willReturnIcon = mIconBridge.getLargeIconForUrl(item.getUrl(),
+        boolean willReturnIcon = mIconBridge.getLargeIconForUrl(mHistoryItem.getUrl(),
                 mContext.getResources().getDimensionPixelSize(R.dimen.open_last_tab_icon_size),
                 (icon, fallbackColor, isFallbackColorDefault, iconType) -> {
-                    setAndShowButton(item.getUrl(), icon, fallbackColor, title);
+                    setAndShowButton(mHistoryItem.getUrl(), icon, fallbackColor, title);
                 });
 
         // False if icon bridge won't call us back.
         if (!willReturnIcon) {
-            setAndShowButton(item.getUrl(), null, R.color.default_icon_color, title);
+            setAndShowButton(mHistoryItem.getUrl(), null, R.color.default_icon_color, title);
         }
         mModel.set(OpenLastTabProperties.OPEN_LAST_TAB_LOAD_SUCCESS, true);
     }
 
     @Override
-    public void onHistoryDeleted() {}
+    public void onHistoryDeleted() {
+        refreshHistoryData();
+    }
 
     @Override
     public void hasOtherFormsOfBrowsingData(boolean hasOtherForms) {}
@@ -172,7 +203,22 @@ class OpenLastTabMediator extends EmptyTabObserver
                     @Override
                     public boolean isItemSupported(
                             @ContextMenuManager.ContextMenuItemId int menuItemId) {
-                        return menuItemId == ContextMenuManager.ContextMenuItemId.ADD_TO_MY_APPS;
+                        return menuItemId == ContextMenuManager.ContextMenuItemId.ADD_TO_MY_APPS
+                                || menuItemId == ContextMenuManager.ContextMenuItemId.REMOVE;
+                    }
+
+                    @Override
+                    public void removeItem() {
+                        mLastRemovedVisitTimestamp = mHistoryItem.getTimestamp();
+                        PostTask.postTask(TaskTraits.USER_VISIBLE, () -> {
+                            SharedPreferences prefs = getSharedPreferences();
+                            prefs.edit()
+                                    .putLong(LAST_REMOVED_VISIT_TIMESTAMP_KEY,
+                                            mLastRemovedVisitTimestamp)
+                                    .apply();
+                        });
+                        mHistoryBridge.markItemForRemoval(mHistoryItem);
+                        mHistoryBridge.removeItems();
                     }
 
                     @Override