Revert of [sql] Use memory-mapped I/O for sql::Connection. (patchset #3 id:40001 of https://codereview.chromium.org/1368533003/ )

Reason for revert:
data race reported by TSan on sql/connection.cc

BUG=537681

Original issue's description:
> [sql] Use memory-mapped I/O for sql::Connection.
>
> sql::Connection::Open*() uses PRAGMA mmap_size to enable SQLite's
> memory-mapped I/O.  Additionally instrument to flush dirty pages from
> the page cache after writes.
>
> [Relands https://crrev.com/9a1948a4d6d4,
> reverted at https://crrev.com/55c3216b15ce ]
>
> BUG=489784, 533682
>
> Committed: https://crrev.com/5c2f4e50d96d8b2ae0ae4a5c7d319e6be3b33bca
> Cr-Commit-Position: refs/heads/master@{#351344}

TBR=rmcilroy@chromium.org,pavely@chromium.org,shess@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=489784, 533682

Review URL: https://codereview.chromium.org/1375583003

Cr-Commit-Position: refs/heads/master@{#351596}

1 files changed, 0 insertions, 80 deletions

diff --git a/sql/connection_unittest.cc b/sql/connection_unittest.cc
index 0038a1d..10a15a8 100644
--- a/sql/connection_unittest.cc
+++ b/sql/connection_unittest.cc
@@ -4,12 +4,10 @@
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
-#include "base/files/memory_mapped_file.h"
 #include "base/files/scoped_file.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/logging.h"
 #include "base/metrics/statistics_recorder.h"
-#include "base/strings/stringprintf.h"
 #include "base/test/histogram_tester.h"
 #include "sql/connection.h"
 #include "sql/correct_sql_test_base.h"
@@ -1300,82 +1298,4 @@ TEST_F(SQLConnectionTest, TimeUpdateTransaction) {
   EXPECT_EQ(0, samples->sum());
 }
 
-// Make sure that OS file writes to a mmap'ed file are reflected in the memory
-// mapping of a memory-mapped file.  Normally SQLite writes to memory-mapped
-// files using memcpy(), which should stay consistent.  Our SQLite is slightly
-// patched to mmap read only, then write using OS file writes.  If the
-// memory-mapped version doesn't reflect the OS file writes, SQLite's
-// memory-mapped I/O should be disabled on this platform.
-#if !defined(MOJO_APPTEST_IMPL)
-TEST_F(SQLConnectionTest, MmapTest) {
-  // Skip the test for platforms which don't enable memory-mapped I/O in SQLite,
-  // or which don't even support the pragma.  The former seems to apply to iOS,
-  // the latter to older iOS.
-  // TODO(shess): Disable test on iOS?  Disable on USE_SYSTEM_SQLITE?
-  {
-    sql::Statement s(db().GetUniqueStatement("PRAGMA mmap_size"));
-    if (!s.Step() || !s.ColumnInt64(0))
-      return;
-  }
-
-  // The test re-uses the database file to make sure it's representative of a
-  // SQLite file, but will be storing incompatible data.
-  db().Close();
-
-  const uint32 kFlags =
-      base::File::FLAG_OPEN|base::File::FLAG_READ|base::File::FLAG_WRITE;
-  char buf[4096];
-
-  // Create a file with a block of '0', a block of '1', and a block of '2'.
-  {
-    base::File f(db_path(), kFlags);
-    ASSERT_TRUE(f.IsValid());
-    memset(buf, '0', sizeof(buf));
-    ASSERT_EQ(f.Write(0*sizeof(buf), buf, sizeof(buf)), (int)sizeof(buf));
-
-    memset(buf, '1', sizeof(buf));
-    ASSERT_EQ(f.Write(1*sizeof(buf), buf, sizeof(buf)), (int)sizeof(buf));
-
-    memset(buf, '2', sizeof(buf));
-    ASSERT_EQ(f.Write(2*sizeof(buf), buf, sizeof(buf)), (int)sizeof(buf));
-  }
-
-  // mmap the file and verify that everything looks right.
-  {
-    base::MemoryMappedFile m;
-    ASSERT_TRUE(m.Initialize(db_path()));
-
-    memset(buf, '0', sizeof(buf));
-    ASSERT_EQ(0, memcmp(buf, m.data() + 0*sizeof(buf), sizeof(buf)));
-
-    memset(buf, '1', sizeof(buf));
-    ASSERT_EQ(0, memcmp(buf, m.data() + 1*sizeof(buf), sizeof(buf)));
-
-    memset(buf, '2', sizeof(buf));
-    ASSERT_EQ(0, memcmp(buf, m.data() + 2*sizeof(buf), sizeof(buf)));
-
-    // Scribble some '3' into the first page of the file, and verify that it
-    // looks the same in the memory mapping.
-    {
-      base::File f(db_path(), kFlags);
-      ASSERT_TRUE(f.IsValid());
-      memset(buf, '3', sizeof(buf));
-      ASSERT_EQ(f.Write(0*sizeof(buf), buf, sizeof(buf)), (int)sizeof(buf));
-    }
-    ASSERT_EQ(0, memcmp(buf, m.data() + 0*sizeof(buf), sizeof(buf)));
-
-    // Repeat with a single '4' in case page-sized blocks are different.
-    const size_t kOffset = 1*sizeof(buf) + 123;
-    ASSERT_NE('4', m.data()[kOffset]);
-    {
-      base::File f(db_path(), kFlags);
-      ASSERT_TRUE(f.IsValid());
-      buf[0] = '4';
-      ASSERT_EQ(f.Write(kOffset, buf, 1), 1);
-    }
-    ASSERT_EQ('4', m.data()[kOffset]);
-  }
-}
-#endif
-
 }  // namespace