Fix: long-tapping a WebAPK in recents shows Chrome.

chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/RecentsPlaceholderActivity.java

Index: chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/RecentsPlaceholderActivity.java
diff --git a/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/RecentsPlaceholderActivity.java b/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/RecentsPlaceholderActivity.java
new file mode 100644
index 0000000000000000000000000000000000000000..f43374e6c6913202597407f45685ae57b3808d1c
--- /dev/null
+++ b/chrome/android/webapk/shell_apk/src/org/chromium/webapk/shell_apk/RecentsPlaceholderActivity.java
@@ -0,0 +1,27 @@
+// Copyright 2017 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.webapk.shell_apk;
+
+import android.app.Activity;
+import android.os.Build;
+import android.os.Bundle;
+
+/**
+ * WebAPK's activity which launches host browser and is shown in recents on L+.
+ */
+public class RecentsPlaceholderActivity extends Activity {
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        if (!LaunchWebApkHelper.launch(this)) {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+                finishAndRemoveTask();
+            } else {
+                finish();
+            }
+        }

[gone, 2017/03/29 18:48:41]

This thing should always finish, shouldn't it?  Otherwise a failed launch
results in an invisible activity that responds to Intent launches when it
shouldn't.

+    }
+}