Add background-wide file metadata cache.

ui/file_manager/file_manager/common/js/importer_common_unittest.js

Index: ui/file_manager/file_manager/common/js/importer_common_unittest.js
diff --git a/ui/file_manager/file_manager/common/js/importer_common_unittest.js b/ui/file_manager/file_manager/common/js/importer_common_unittest.js
index d013f193931e28f25c2981cf72e7a4591d8d13f9..7d14b8f0d53868207b41abd98cc9e9c1b1a34425 100644
--- a/ui/file_manager/file_manager/common/js/importer_common_unittest.js
+++ b/ui/file_manager/file_manager/common/js/importer_common_unittest.js
@@ -246,21 +246,6 @@ function testDeflateAppUrl() {
       'Deflated then inflated URLs must match original URL.');
 };
 
-function testCreateMetadataHashcode(callback) {
-  var promise = importer.createMetadataHashcode(cameraFileEntry)
-      .then(
-          function(hashcode) {
-            // Note that the expression matches at least 4 numbers
-            // in the last segment, since we hard code the byte
-            // size in our test file to a four digit size.
-            // In reality it will vary.
-            assertEquals(0, hashcode.search(/[0-9]{9,}_[0-9]{4,}/),
-                'Hashcode (' + hashcode + ') does not match next pattern.');
-          });
-
-  reportPromise(promise, callback);
-}
-
 function testHasMediaDirectory(callback) {
   var dir = createDirectoryEntry(sdVolume, '/DCIM');
   var promise = importer.hasMediaDirectory(sdVolume.fileSystem.root)