Changes caching logic of mojo java apps

mojo/runner/android/apk/src/org/chromium/mojo/shell/ShellMain.java

Index: mojo/runner/android/apk/src/org/chromium/mojo/shell/ShellMain.java
diff --git a/mojo/runner/android/apk/src/org/chromium/mojo/shell/ShellMain.java b/mojo/runner/android/apk/src/org/chromium/mojo/shell/ShellMain.java
index 46af7465ca152e7074d376cfad5115a2ab511bbe..4af0974752189458820a133dea7b574a183adcb9 100644
--- a/mojo/runner/android/apk/src/org/chromium/mojo/shell/ShellMain.java
+++ b/mojo/runner/android/apk/src/org/chromium/mojo/shell/ShellMain.java
@@ -27,7 +27,8 @@ import java.util.List;
 public class ShellMain {
     private static final String TAG = "ShellMain";
 
-    // Directory where applications bundled with the shell will be extracted.
+    // Directory where applications cached with the shell will be extracted.
+    // TODO(sky): rename this to CACHED_APP_DIRECTORY.
     private static final String LOCAL_APP_DIRECTORY = "local_apps";
     // The mojo_shell library is also an executable run in forked processes when running
     // multi-process.
@@ -72,9 +73,13 @@ public class ShellMain {
         if (sInitialized) return;
         File localAppsDir = getLocalAppsDir(applicationContext);
         try {
+            final File timestamp =
+                    FileHelper.prepareDirectoryForAssets(applicationContext, localAppsDir);
             for (String assetPath : getAssetsList(applicationContext)) {
-                FileHelper.extractFromAssets(applicationContext, assetPath, localAppsDir, false);
+                FileHelper.extractFromAssets(
+                        applicationContext, assetPath, localAppsDir, FileHelper.FileType.PERMANENT);
             }
+            FileHelper.createTimestampIfNecessary(timestamp);
             File mojoShell = new File(applicationContext.getApplicationInfo().nativeLibraryDir,
                     MOJO_SHELL_EXECUTABLE);
 
@@ -111,7 +116,7 @@ public class ShellMain {
         nativeAddApplicationURL(url);
     }
 
-    private static File getLocalAppsDir(Context context) {
+    static File getLocalAppsDir(Context context) {
         return context.getDir(LOCAL_APP_DIRECTORY, Context.MODE_PRIVATE);
     }
 
@@ -128,7 +133,7 @@ public class ShellMain {
      * Initializes the native system. This API should be called only once per process.
      **/
     private static native void nativeInit(Context context, String mojoShellPath,
-            String[] parameters, String bundledAppsDirectory, String tmpDir);
+            String[] parameters, String cachedAppsDirectory, String tmpDir);
 
     private static native boolean nativeStart();