Add a data source field for volumes.

chrome/test/data/extensions/api_test/file_system_provider/get_all/test.js

Index: chrome/test/data/extensions/api_test/file_system_provider/get_all/test.js
diff --git a/chrome/test/data/extensions/api_test/file_system_provider/get_all/test.js b/chrome/test/data/extensions/api_test/file_system_provider/get_all/test.js
index a0fa062e165918d8deadbd62fde6fe466b922a6f..993925fc11cecb1620724c1be21d332dca8803ba 100644
--- a/chrome/test/data/extensions/api_test/file_system_provider/get_all/test.js
+++ b/chrome/test/data/extensions/api_test/file_system_provider/get_all/test.js
@@ -86,6 +86,8 @@ function runTests() {
                                     fileSystems[0].displayName);
                                 chrome.test.assertTrue(
                                     fileSystems[0].writable);
+                                chrome.test.assertEq(
+                                    'NETWORK', fileSystems[0].source);
                                 chrome.test.assertEq(2,
                                     fileSystems[0].openedFilesLimit);
                               }));
@@ -100,6 +102,8 @@ function runTests() {
                                     test_util.FILE_SYSTEM_NAME,
                                     fileSystem.displayName);
                                 chrome.test.assertTrue(fileSystem.writable);
+                                chrome.test.assertEq(
+                                    'NETWORK', fileSystem.source);
                                 chrome.test.assertEq(2,
                                     fileSystem.openedFilesLimit);
                                 }));
@@ -113,7 +117,7 @@ function runTests() {
                 function(error) {
                   chrome.test.fail(error.name);
                 });
-          }), {writable: true, openedFilesLimit: 2});
+          }), {writable: true, openedFilesLimit: 2, source: 'NETWORK'});
     },
 
     // Verifies that after unmounting, the file system is not available in