Fix up _some_web app directory StrictMode violations

chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappManagedActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappManagedActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappManagedActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappManagedActivity.java
index 13798645afd2f6e947b93ad1d0c87495ef619cf3..8bab1fc109de67ef27cf1c788d67979084cb0fea 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappManagedActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappManagedActivity.java
@@ -4,8 +4,6 @@
 
 package org.chromium.chrome.browser.webapps;
 
-import java.io.File;
-
 /**
  * Type of WebappActivity that has the ability to swap out the webapp it is currently showing for a
  * new one. This is necessary on Android versions older than L because the framework had no way of
@@ -29,8 +27,8 @@ public abstract class WebappManagedActivity extends WebappActivity {
     }
 
     @Override
-    protected File getActivityDirectory() {
-        return WebappDirectoryManager.getWebappDirectory(String.valueOf(mActivityIndex));
+    protected String getId() {
+        return String.valueOf(mActivityIndex);
     }
 
     /**