Revert 243344 "IndexedDB: Fix cursor prefetching edge cases"

Revert 243344 "IndexedDB: Fix cursor prefetching edge cases"

> IndexedDB: Fix cursor prefetching edge cases
> 
> Cursor prefetch caches must be discarded when other
> requests are made to ensure proper request sequencing.
> Two edge cases were handled improperly if new records
> was written just ahead of the cursor.
> 
> * A reset occurring before the prefetch results were
> received would be ignored; since the newly records
> weren't in the prefetch data, the cursor wouldn't see
> them.
> 
> * A reset occurring after the results are received
> would back up the cursor to before the new records,
> even though the prefetch itself is a "continue"
> and advanced past them already.
> 
> The fix is to reset the cache on receipt if necessary,
> and to ensure the reset state accounts for the implicit
> advance.
> 
> BUG=331570
> 
> Review URL: https://codereview.chromium.org/124323002

TBR=jsbell@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=243359

[ccameron, 2014-01-07 19:34:06]

Committed patchset #1 manually as r243359.

[Lei Zhang, 2014-01-07 22:01:22]

The reason for the revert is below. Valgrind detected it as well, FWIW.

ERROR: LeakSanitizer: detected memory leaks

Direct leak of 16 byte(s) in 1 object(s) allocated from:
    #0 0x496039 in operator new(unsigned long)
/usr/local/google/work/chromium/src/third_party/llvm/projects/compiler-rt/lib/asan/asan_new_delete.cc:52
    #1 0x15829c4 in content::WebIDBCursorImplTest_PrefetchReset_Test::TestBody()
content/child/indexed_db/webidbcursor_impl_unittest.cc:299
    #2 0x2cbf97a in testing::Test::Run() testing/gtest/src/gtest.cc:2061
    #3 0x2cc1a3d in testing::TestInfo::Run() testing/gtest/src/gtest.cc:2237
    #4 0x2cc2a42 in testing::TestCase::Run() testing/gtest/src/gtest.cc:2344
    #5 0x2cd3cc5 in testing::internal::UnitTestImpl::RunAllTests()
testing/gtest/src/gtest.cc:4065
    #6 0x2cd320e in
HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl, bool>
testing/gtest/src/gtest.cc:2045
    #7 0x2cd320e in testing::UnitTest::Run() testing/gtest/src/gtest.cc:3697
    #8 0x2c5115e in RUN_ALL_TESTS testing/gtest/include/gtest/gtest.h:2231
    #9 0x2c5115e in base::TestSuite::Run() base/test/test_suite.cc:213
    #10 0x2c44bc3 in Run base/callback.h:401
    #11 0x2c44bc3 in base::(anonymous namespace)::LaunchUnitTestsInternal(int,
char**, base::Callback<int ()> const&, int)
base/test/launcher/unit_test_launcher.cc:506
    #12 0x190b24e in main content/test/run_all_unittests.cc:14
    #13 0x7f935cb8876c in __libc_start_main
/build/buildd/eglibc-2.15/csu/libc-start.c:226

[jsbell, 2014-01-07 22:06:53]

Yep, already fixed (was a test-only leak) and resubmitted to the CQ.

Thanks folks!