Expose computation of md5 content checksums for files via a file manager private API.

chrome/test/data/extensions/api_test/file_browser/content_checksum_test/test.js

Index: chrome/test/data/extensions/api_test/file_browser/content_checksum_test/test.js
diff --git a/chrome/test/data/extensions/api_test/file_browser/content_checksum_test/test.js b/chrome/test/data/extensions/api_test/file_browser/content_checksum_test/test.js
new file mode 100644
index 0000000000000000000000000000000000000000..35e08f5221923aaea4a8c14da5c2a2a1e59a7dfc
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/file_browser/content_checksum_test/test.js
@@ -0,0 +1,75 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.

[mtomasz, 2015/01/08 00:38:40]

(c) 2013 -> 2014

[Ben Kwa, 2015/01/08 19:29:14]

2015!

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+ * The test file system should be created and populated before running the test
+ * extension.
+ *
+ * The only file used right now is <root>/test_dir/test_file.txt.
+ */
+
+// This is a golden value computed using the md5sum command line tool.
+var kExpectedHash = 'a3dfffb5a580272fb8986611a9dbd166';
+
+function initTests(callback) {

[mtomasz, 2015/01/08 00:38:40]

I think this can be greatly simplified. If we only care about the file system
with testing volume, not Drive.
We could simply iterate over the volume metadata list and request the file
system which has 'testing' substring. No need to sort, collect any tests, etc.

[Ben Kwa, 2015/01/08 19:29:14]

Ah, ok.  Thanks for clarifying - I wasn't sure what was and wasn't needed.  Much
cleaner now.

+  chrome.fileManagerPrivate.getVolumeMetadataList(function(volumeMetadataList) {
+    var possibleVolumeTypes = ['testing', 'drive'];
+
+    var sortedVolumeMetadataList = volumeMetadataList.filter(function(volume) {
+      return possibleVolumeTypes.indexOf(volume.volumeType) != -1;
+    }).sort(function(volumeA, volumeB) {
+      return possibleVolumeTypes.indexOf(volumeA.volumeType) >
+             possibleVolumeTypes.indexOf(volumeB.volumeType);
+    });
+
+    if (sortedVolumeMetadataList.length == 0) {
+      callback(null, 'No volumes available, which could be used for testing.');
+      return;
+    }
+
+    chrome.fileManagerPrivate.requestFileSystem(
+        sortedVolumeMetadataList[0].volumeId,
+        function(fileSystem) {
+          if (!fileSystem) {
+            callback(null, 'Failed to acquire the testing volume.');
+            return;
+          }
+
+          var testsToRun = collectTestsForVolumeId(
+              sortedVolumeMetadataList[0].volumeId, fileSystem);
+          callback(testsToRun, 'Success.');
+        });
+  });
+}
+
+function collectTestsForVolumeId(volumeId, fileSystem) {
+  console.log(volumeId);
+  var testsToRun = [];
+
+  testsToRun.push(function quickTest() {
+    fileSystem.root.getFile(
+        'test_dir/test_file.txt',
+        {create: false},
+        function(entry) {
+          chrome.fileManagerPrivate.computeChecksum(
+              entry.toURL(),
+              chrome.test.callbackPass(function(result) {
+                chrome.test.assertEq(kExpectedHash, result);
+                }));
+        },
+        chrome.test.fail);
+  });
+
+  return testsToRun;
+}
+
+// Trigger the tests.
+initTests(function(testsToRun, errorMessage) {
+  if (!testsToRun) {
+    chrome.test.notifyFail('Failed to initialize tests: ' + errorMessage);
+    return;
+  }
+
+  chrome.test.runTests(testsToRun);
+});