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";

[ppi, 2014/12/22 12:02:25]

nit: everything is Mojo in this world, I would probably call it "FileHelper"

[qsr, 2014/12/22 12:44:19]

 Everything is mojo, but this is what appear in adb logcat that contains all the
log of all the application on the device. Prefixing this with mojo helps finding
those logs.

+
     // 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

[ppi, 2014/12/22 12:02:25]

Maybe use the javadoc style (matching other per-method comments in this
package).

[qsr, 2014/12/22 12:44:19]

Done.

+    // the resource paks were extracted from. Returns null if a timestamp was found

[ppi, 2014/12/22 12:02:25]

what is resource pak? should we say "assets", or do we mean resources here (as
per the apk terminology)?

[qsr, 2014/12/22 12:44:19]

 Because I copied paste this comment. Fixed.

+    // and it indicates that the resources match the current APK. Otherwise returns
+    // a String that represents the filename of a timestamp to create.

[ppi, 2014/12/22 12:02:25]

This calls for splitting this up - can we extract the method to compute the
expected timestamp and have another to check if the files match the expected
one?

[qsr, 2014/12/22 12:44:19]

 As discussed, I prefer not to cut this method because it would otherwise
obliged me to either keep more state when using it, or to access the disk more.

+    private static String checkAssetTimestamp(Context context, File outputDir) {
+        final String timestampPrefix = "asset_timestamp-";

[ppi, 2014/12/22 12:02:25]

let's make it private static final field like the others?

[qsr, 2014/12/22 12:44:19]

Done.

+        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.

[ppi, 2014/12/22 12:02:25]

nit: capitalize the first word.

[qsr, 2014/12/22 12:44:20]

Done.

+        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.

[ppi, 2014/12/22 12:02:25]

nit: s/Worst case/In the worst case/

[qsr, 2014/12/22 12:44:19]

Done.

+                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();
     }
 }