Add cache test.

chrome/test/data/indexeddb/perf_shared.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 window.indexedDB = window.indexedDB || window.webkitIndexedDB ||
     window.mozIndexedDB || window.msIndexedDB;
 window.IDBKeyRange = window.IDBKeyRange || window.webkitIDBKeyRange;
 
 var automation = {
   results: {}
@@ skipping 293 matching lines @@
   for (var i in objectStoreNames) {
     var os = transaction.objectStore(objectStoreNames[i]);
     for (var j = 0; j < numPuts; ++j) {
       var rand = Math.floor(Math.random() * numKeys);
       var request = os.put(getValue(rand), getKey(rand));
       request.onerror = onError;
     }
   }
 }
 
+function getSpecificValues(transaction, objectStoreNames, indexName, keys) {
+  for (var i in objectStoreNames) {
+    var os = transaction.objectStore(objectStoreNames[i]);
+    var source = os;
+    if (indexName)
+      source = source.index(indexName);
+    for (var j = 0; j < keys.length; ++j) {
+      var request = source.get(keys[j]);
+      request.onerror = onError;

[jsbell, 2012/08/09 17:58:18]

This doesn't verify that a value was returned (success event with result
non-null vs. null), which is *mostly* fine for the test itself, but means we may
not catch logic errors in the test where we're requesting keys that don't exist.

Although it shouldn't make a difference now, I could imagine a future caching
scheme where the min/max keys of the source were known and out-of-range requests
were optimized, and/or the caching behavior of hits vs. misses was different
(e.g. if hits were cached but misses were not). Without verifying that a value
was read we might be testing the wrong thing.

(That may inspire a few more perf test cases as well.)

[ericu, 2012/08/15 17:56:22]

Added it in a couple of places.

+    }
+  }
+}
+
 // getKey should be deterministic, as we assume that a cursor that starts at
 // getKey(X) and runs through getKey(X + K) has exactly K values available.
 // This is annoying to guarantee generally when using an index, so we avoid both
 // ends of the key space just in case and use simple indices.
 // TODO(ericu): Figure out if this can be simplified and we can remove uses of
 // getObjectValue in favor of getNFieldObjectValue.
 function getValuesFromCursor(
     transaction, inputObjectStoreName, numReads, numKeys, indexName, getKey,
     readKeysOnly, outputObjectStoreName) {
   assert(2 * numReads < numKeys);
@@ skipping 29 matching lines @@
         // outside its range.
         oos.put(cursor.value, numKeys + Math.random());
       values.push({key: cursor.key, value: cursor.value});
       cursor.continue();
     } else {
       assert(!numReadsLeft);
     }
   }
   request.onerror = onError;
 }