Delete tab state files when the user explicitly closes a CCT.

chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabTabPersistencePolicy.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.customtabs;
 
 import android.app.Activity;
 import android.os.AsyncTask;
 import android.os.StrictMode;
 import android.util.Pair;
@@ skipping 187 matching lines @@
     @Override
     public void notifyStateLoaded(int tabCountAtStartup) {
     }
 
     @Override
     public void destroy() {
         mDestroyed = true;
     }
 
     /**
+     * Triggers an async deletion of the tab state metadata file.
+     */
+    public void deleteMetadataStateFileAsync() {
+        AsyncTask.SERIAL_EXECUTOR.execute(new Runnable() {
+            @Override
+            public void run() {
+                File stateDir = getOrCreateStateDirectory();
+                File metadataFile = new File(stateDir, getStateFileName());
+                if (metadataFile.exists() && !metadataFile.delete()) {
+                    Log.e(TAG, "Failed to delete file: " + metadataFile);
+                }
+            }
+        });
+    }
+
+    /**
      * Given a list of metadata files, determine which are applicable for deletion based on the
      * deletion strategy of Custom Tabs.
      *
      * @param currentTimeMillis The current time in milliseconds
      *                          ({@link System#currentTimeMillis()}.
      * @param allMetadataFiles The complete list of all metadata files to check.
      * @return The list of metadata files that are applicable for deletion.
      */
     protected static List<File> getMetadataFilesForDeletion(
             long currentTimeMillis, List<File> allMetadataFiles) {
@@ skipping 169 matching lines @@
                         new BufferedInputStream(new FileInputStream(metadataFile)));
                 TabPersistentStore.readSavedStateFile(stream, null, tabIds, false);
             } catch (Exception e) {
                 Log.e(TAG, "Unable to read state for " + metadataFile.getName() + ": " + e);
             } finally {
                 StreamUtil.closeQuietly(stream);
             }
         }
     }
 }