Fix incorrect computation of LastModified in SimpleCache,

net/disk_cache/backend_unittest.cc

 // 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.
 
 #include <stdint.h>
 
 #include "base/files/file.h"
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial.h"
@@ skipping 3980 matching lines @@
   // because that would advance the cache directory mtime and invalidate the
   // index.
   entry2->Doom();
   entry2->Close();
 
   DisableFirstCleanup();
   InitCache();
   EXPECT_EQ(disk_cache::SimpleIndex::INITIALIZE_METHOD_LOADED,
             simple_cache_impl_->index()->init_method());
 }
+
+TEST_F(DiskCacheBackendTest, SimpleLastModified) {

[jkarlin, 2017/04/21 13:48:33]

Please add a comment describing what this test is doing and link to the crbug
it's related to

[Maks Orlovich, 2017/04/21 15:12:52]

Done.

+  SetSimpleCacheMode();
+  InitCache();
+  std::string key1 = GenerateKey(true);
+  std::string key2 = GenerateKey(true);
+
+  disk_cache::Entry* entry1;
+  ASSERT_THAT(CreateEntry(key1, &entry1), IsOk());
+
+  // Make the Create complete --- SimpleCache can handle it optimistically,
+  // and if we let it go fully async then trying to flush the Close might just
+  // flush the Create.
+  disk_cache::SimpleBackendImpl::FlushWorkerPoolForTesting();
+  base::RunLoop().RunUntilIdle();
+
+  entry1->Close();
+
+  // Make the ::Close actually complete, since it is asynchronous.
+  disk_cache::SimpleBackendImpl::FlushWorkerPoolForTesting();
+  base::RunLoop().RunUntilIdle();
+
+  Time entry1_timestamp = Time::NowFromSystemTime();
+
+  // Don't want AddDelay since it sleep 1s(!) for SimpleCache, and we don't
+  // care about reduced precision in index here.
+  while (base::Time::Now() <=

[jkarlin, 2017/04/21 13:48:33]

Also use NowFromSystemTime here?

[Maks Orlovich, 2017/04/21 15:12:52]

Done.

+         (entry1_timestamp + base::TimeDelta::FromMilliseconds(10))) {
+    base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(1));
+  }
+
+  disk_cache::Entry* entry2;
+  ASSERT_THAT(CreateEntry(key2, &entry2), IsOk());
+  entry2->Close();
+  disk_cache::SimpleBackendImpl::FlushWorkerPoolForTesting();
+  base::RunLoop().RunUntilIdle();
+
+  disk_cache::Entry* reopen_entry1;
+  ASSERT_THAT(OpenEntry(key1, &reopen_entry1), IsOk());
+
+  // This shouldn't pick up entry2's write time incorrectly.
+  EXPECT_LE(reopen_entry1->GetLastModified(), entry1_timestamp);
+  reopen_entry1->Close();
+}