Add cache test.

chrome/test/data/indexeddb/perf_test.js

Index: chrome/test/data/indexeddb/perf_test.js
diff --git a/chrome/test/data/indexeddb/perf_test.js b/chrome/test/data/indexeddb/perf_test.js
index 708fc3f625b1286f9defbc7c16abc227357b5c3a..244c3d7966e83cd2ef03c056ef9a550f9b2fd463 100644
--- a/chrome/test/data/indexeddb/perf_test.js
+++ b/chrome/test/data/indexeddb/perf_test.js
@@ -77,6 +77,14 @@ var tests = [
 // Make large batches of random writes into a store with many indices, triggered
 // by periodic setTimeout calls.
   [testSporadicWrites, 500, 10],
+// Make a small bunch of batches of reads of the same keys from an object store.
+  [testReadCache, 10, kDontUseIndex],
+// Make a bunch of batches of reads of the same keys from an index.
+  [testReadCache, 50, kUseIndex],
+// Make a small bunch of batches of reads of the same keys from an object store.
+  [testReadCache, 10, kDontUseIndex],
+// Make a bunch of batches of reads of the same keys from an index.
+  [testReadCache, 50, kUseIndex],
 // Create and delete an index on a store that already contains data [produces
 // a timing result for each of creation and deletion].
   [testCreateAndDeleteIndex, 5000]
@@ -243,6 +251,70 @@ function testRandomReadsAndWrites(
   }
 }
 
+function testReadCache(numTransactions, useIndexForReads, onTestComplete) {
+  var numKeys = 10000;
+  var numReadsPerTransaction = 50;
+  var numTransactionsLeft = numTransactions;
+  var indexName;
+  if (useIndexForReads)
+    indexName = "index";
+  var testName = getDisplayName(arguments);
+  var objectStoreNames = ["store"];
+  var numTransactionsRunning;
+  var keys = [];
+
+  for (var i=0; i < numReadsPerTransaction; ++i) {
+    keys.push(getSimpleKey(Math.floor(Math.random() * numKeys)));
+  }
+
+  automation.setStatus("Creating database.");
+  var options;
+  if (useIndexForReads) {
+    options = [{
+      indexName: indexName,
+      indexKeyPath: "",
+      indexIsUnique: false,
+      indexIsMultiEntry: false,
+    }];
+  }
+  createDatabase(testName, objectStoreNames, onCreated, onError, options);
+
+  function onCreated(db) {
+    automation.setStatus("Setting up test database.");
+    var transaction = getTransaction(db, objectStoreNames, "readwrite",
+        function() { onSetupComplete(db); });
+    putLinearValues(transaction, objectStoreNames, numKeys, getSimpleKey,
+        function () { return "test value"; });

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

Nit: space between function keyword and ()

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

Done.

+  }
+
+  var completionFunc;
+  function onSetupComplete(db) {
+    automation.setStatus("Setup complete.");
+    completionFunc =
+        getCompletionFunc(db, testName, Date.now(), onTestComplete);
+    runOneBatch(db);
+  }
+
+  function runOneBatch(db) {

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

This runOneBatch() pattern seems to be re-used in many tests. Factor out?

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

It's used in 3 places, but one is actually different than the others [running
the transactions from a timer instead of just chaining them together].  I pulled
out the common pattern from the 2 that matched, and that'll probably get reused
in a bunch more tests.

+    if (numTransactionsLeft <= 0) {
+      return;
+    }
+    --numTransactionsLeft;
+    ++numTransactionsRunning;
+    var transaction = getTransaction(db, objectStoreNames, "readonly",
+        function() {
+          assert(!--numTransactionsRunning);
+          if (numTransactionsLeft <= 0) {
+            completionFunc();
+          } else {
+            runOneBatch(db);
+          }
+        });
+
+    getSpecificValues(transaction, objectStoreNames, indexName, keys);
+  }
+}
+
 function testCreateAndDeleteIndex(numKeys, onTestComplete) {
   var testName = getDisplayName(arguments);
   var objectStoreNames = ["store"];