Run shell tests on android.

shell/android/apk/src/org/chromium/mojo/shell/FileHelper.java

Index: shell/android/apk/src/org/chromium/mojo/shell/FileHelper.java
diff --git a/shell/android/apk/src/org/chromium/mojo/shell/FileHelper.java b/shell/android/apk/src/org/chromium/mojo/shell/FileHelper.java
index adc747e4756970f5033091c2aa36c4c04d0ec9f4..8af64d5e610693aafaa4bf763e7f9ffa0787f9b2 100644
--- a/shell/android/apk/src/org/chromium/mojo/shell/FileHelper.java
+++ b/shell/android/apk/src/org/chromium/mojo/shell/FileHelper.java
@@ -5,6 +5,9 @@
 package org.chromium.mojo.shell;
 
 import android.content.Context;
+import android.content.pm.PackageInfo;
+import android.content.pm.PackageManager;
+import android.util.Log;
 
 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
@@ -12,6 +15,7 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
+import java.io.FilenameFilter;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -22,13 +26,67 @@ import java.util.zip.ZipInputStream;
  * Helper methods for file extraction from APK assets and zip archives.
  */
 class FileHelper {
+    public static final String TAG = "MojoFileHelper";
+
     // Size of the buffer used in streaming file operations.
     private static final int BUFFER_SIZE = 1024 * 1024;
     // Prefix used when naming temporary files.
     private static final String TEMP_FILE_PREFIX = "temp-";
 
-    static File extractFromAssets(Context context, String assetName, File outputDirectory,
+    // Looks for a timestamp file on disk that indicates the version of the APK that
+    // the resource paks were extracted from. Returns null if a timestamp was found
+    // and it indicates that the resources match the current APK. Otherwise returns
+    // a String that represents the filename of a timestamp to create.
+    private static String checkAssetTimestamp(Context context, File outputDir) {
+        final String timestampPrefix = "asset_timestamp-";
+        PackageManager pm = context.getPackageManager();
+        PackageInfo pi = null;
+
+        try {
+            pi = pm.getPackageInfo(context.getPackageName(), 0);
+        } catch (PackageManager.NameNotFoundException e) {
+            return timestampPrefix;
+        }
+
+        if (pi == null) {
+            return timestampPrefix;
+        }
+
+        String expectedTimestamp = timestampPrefix + pi.versionCode + "-" + pi.lastUpdateTime;
+
+        String[] timestamps = outputDir.list(new FilenameFilter() {
+                @Override
+            public boolean accept(File dir, String name) {
+                return name.startsWith(timestampPrefix);
+            }
+        });
+
+        if (timestamps.length != 1) {
+            // If there's no timestamp, nuke to be safe as we can't tell the age of the files.
+            // If there's multiple timestamps, something's gone wrong so nuke.
+            return expectedTimestamp;
+        }
+
+        if (!expectedTimestamp.equals(timestamps[0])) {
+            return expectedTimestamp;
+        }
+
+        // timestamp file is already up-to date.
+        return null;
+    }
+
+    public static File extractFromAssets(Context context, String assetName, File outputDirectory,
             boolean useTempFile) throws IOException, FileNotFoundException {
+        String timestampFile = null;
+        if (!useTempFile) {
+            timestampFile = checkAssetTimestamp(context, outputDirectory);
+            if (timestampFile != null) {
+                for (File child : outputDirectory.listFiles()) {
+                    deleteRecursively(child);
+                }
+            }
+        }
+
         File outputFile;
         if (useTempFile) {
             // Make the original filename part of the temp file name.
@@ -37,12 +95,28 @@ class FileHelper {
             outputFile = File.createTempFile(TEMP_FILE_PREFIX, suffix, outputDirectory);
         } else {
             outputFile = new File(outputDirectory, assetName);
+            if (outputFile.exists()) {
+                return outputFile;
+            }
         }
 
         BufferedInputStream inputStream = new BufferedInputStream(
                 context.getAssets().open(assetName));
-        writeStreamToFile(inputStream, outputFile);
-        inputStream.close();
+        try {
+            writeStreamToFile(inputStream, outputFile);
+        } finally {
+            inputStream.close();
+        }
+
+        if (timestampFile != null) {
+            try {
+                new File(outputDirectory, timestampFile).createNewFile();
+            } catch (IOException e) {
+                // Worst case we don't write a timestamp, so we'll re-extract the asset next time.
+                Log.w(TAG, "Failed to write asset timestamp!");
+            }
+        }
+
         return outputFile;
     }
 
@@ -87,10 +161,13 @@ class FileHelper {
             throws IOException {
         byte[] buffer = new byte[BUFFER_SIZE];
         OutputStream outputStream = new BufferedOutputStream(new FileOutputStream(outputFile));
-        int read;
-        while ((read = inputStream.read(buffer, 0, BUFFER_SIZE)) > 0) {
-            outputStream.write(buffer, 0, read);
+        try {
+            int read;
+            while ((read = inputStream.read(buffer, 0, BUFFER_SIZE)) > 0) {
+                outputStream.write(buffer, 0, read);
+            }
+        } finally {
+            outputStream.close();
         }
-        outputStream.close();
     }
 }