Migrate share activity registration code to ShareHelper

chrome/android/java/src/org/chromium/chrome/browser/share/ShareHelper.java

Index: chrome/android/java/src/org/chromium/chrome/browser/share/ShareHelper.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/share/ShareHelper.java b/chrome/android/java/src/org/chromium/chrome/browser/share/ShareHelper.java
index 97583b682427c1491325995f4a6fa8c3e7c6c11d..15620f1f46a6c0cd1b99d1fc2dae556e8e4c5858 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/share/ShareHelper.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/share/ShareHelper.java
@@ -26,6 +26,7 @@ import android.graphics.drawable.Drawable;
 import android.net.Uri;
 import android.os.AsyncTask;
 import android.os.Build;
+import android.os.StrictMode;
 import android.support.annotation.Nullable;
 import android.support.v7.app.AlertDialog;
 import android.text.TextUtils;
@@ -35,17 +36,21 @@ import android.view.View;
 import android.widget.AdapterView;
 import android.widget.AdapterView.OnItemClickListener;
 
+import org.chromium.base.ActivityState;
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.ApplicationState;
 import org.chromium.base.ApplicationStatus;
+import org.chromium.base.ApplicationStatus.ActivityStateListener;
 import org.chromium.base.Callback;
 import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
 import org.chromium.base.StreamUtil;
+import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.annotations.SuppressFBWarnings;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.chrome.R;
+import org.chromium.chrome.browser.printing.PrintShareActivity;
 import org.chromium.components.dom_distiller.core.DomDistillerUrlUtils;
 import org.chromium.ui.UiUtils;
 
@@ -53,7 +58,9 @@ import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
@@ -104,6 +111,12 @@ public class ShareHelper {
     /** If non-null, will be used instead of the real activity. */
     private static FakeIntentReceiver sFakeIntentReceiverForTesting;
 
+    /** Variables for adding activities dynamically to share picker intent. */
+    private static Set<Activity> sPendingShareActivities =
+            Collections.synchronizedSet(new HashSet<Activity>());
+    private static ActivityStateListener sStateListener;
+    private static AsyncTask<Void, Void, Void> sStateChangeTask;
+
     private ShareHelper() {}
 
     private static void fireIntent(Activity activity, Intent intent) {
@@ -681,4 +694,109 @@ public class ShareHelper {
         if (packageName == null || className == null) return null;
         return new ComponentName(packageName, className);
     }
+
+    /**
+     * Enable the print sharing option.
+     *
+     * @param activity The activity that will be triggering the share action.  The activitiy's
+     *                 state will be tracked to disable the print option when the share operation
+     *                 has been completed.
+     * @param callback The callback to be triggered after the print option has been enabled.  This
+     *                 may or may not be synchronous depending on whether this will require
+     *                 interacting with the Android framework.
+     */
+    public static void enablePrintShareOption(final Activity activity, final Runnable callback) {

[Ted C, 2017/02/11 00:22:27]

Don't make this specific to print.  In general, this class shouldn't know
anything about print.

Call it something like:
enableOptionalShareActivities(...)

Then we'll need to pass something like List<Class<? extends Activity>>
shareActivities as a param since we shouldn't hardcode PrintShareActivity below.

And if we have to pass two activity-like params here, let's change the current
activity param to do something like triggeringActivity

+        ThreadUtils.assertOnUiThread();
+
+        if (sStateListener == null) {
+            sStateListener = new ActivityStateListener() {
+                @Override
+                public void onActivityStateChange(Activity activity, int newState) {
+                    if (newState == ActivityState.PAUSED) return;
+                    unregisterActivity(activity);
+                }
+            };
+        }
+        ApplicationStatus.registerStateListenerForAllActivities(sStateListener);
+        boolean wasEmpty = sPendingShareActivities.isEmpty();
+        sPendingShareActivities.add(activity);
+
+        waitForPendingStateChangeTask();
+        if (wasEmpty) {
+            sStateChangeTask = new AsyncTask<Void, Void, Void>() {
+                @Override
+                protected Void doInBackground(Void... params) {
+                    if (sPendingShareActivities.isEmpty()) return null;
+
+                    activity.getPackageManager().setComponentEnabledSetting(
+                            new ComponentName(activity, PrintShareActivity.class),
+                            PackageManager.COMPONENT_ENABLED_STATE_ENABLED,
+                            PackageManager.DONT_KILL_APP);
+                    return null;
+                }
+
+                @Override
+                protected void onPostExecute(Void result) {
+                    if (sStateChangeTask == this) {
+                        sStateChangeTask = null;
+                    } else {
+                        waitForPendingStateChangeTask();
+                    }
+                    callback.run();
+                }
+            }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+        } else {
+            callback.run();
+        }
+    }
+
+    /**
+     * Disables Components after Share Chooser is done.
+     */
+    public static void unregisterActivity(final Activity activity) {

[Ted C, 2017/02/11 00:22:27]

This name doesn't really make sense IMO.  What activity are you unregistering? 
When it was private (and in a much smaller class), I think it was easier to
grok.

Maybe something like:
disableOptionalShareActivities(final Activity triggeringActivity);

Then you'll want javadoc describing the input and that it is the activity that
initially triggered the share (to help differentiate from the share activities
being enabled).

And since you shouldn't know about print, you'll need to keep a List/Set of the
enabled components to disable here.

+        ThreadUtils.assertOnUiThread();
+
+        sPendingShareActivities.remove(activity);
+        if (!sPendingShareActivities.isEmpty()) return;
+        ApplicationStatus.unregisterActivityStateListener(sStateListener);
+
+        waitForPendingStateChangeTask();
+        sStateChangeTask = new AsyncTask<Void, Void, Void>() {
+            @Override
+            protected Void doInBackground(Void... params) {
+                if (!sPendingShareActivities.isEmpty()) return null;
+
+                activity.getPackageManager().setComponentEnabledSetting(
+                        new ComponentName(activity, PrintShareActivity.class),
+                        PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
+                        PackageManager.DONT_KILL_APP);
+                return null;
+            }
+
+            @Override
+            protected void onPostExecute(Void result) {
+                if (sStateChangeTask == this) sStateChangeTask = null;
+            }
+        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+    }
+
+    /**
+     * Waits for any pending state change operations to be completed.
+     *
+     * This will avoid timing issues described here: crbug.com/649453.
+     */
+    private static void waitForPendingStateChangeTask() {
+        ThreadUtils.assertOnUiThread();
+
+        if (sStateChangeTask == null) return;
+        StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
+        try {
+            sStateChangeTask.get();
+            sStateChangeTask = null;
+        } catch (InterruptedException | ExecutionException e) {
+            Log.e(TAG, "Print state change task did not complete as expected");
+        } finally {
+            StrictMode.setThreadPolicy(oldPolicy);
+        }
+    }
 }