Remove memory corruption testing from base::File().

base/files/file_posix.cc

Index: base/files/file_posix.cc
diff --git a/base/files/file_posix.cc b/base/files/file_posix.cc
index 7fb617c3f9daab5cc0494cb63e54ddc7a3eb1a65..a5aee01aa2935f3d2e1110c1822d44b6cabe8217 100644
--- a/base/files/file_posix.cc
+++ b/base/files/file_posix.cc
@@ -420,49 +420,6 @@ File::Error File::OSErrorToFileError(int saved_errno) {
   }
 }
 
-File::MemoryCheckingScopedFD::MemoryCheckingScopedFD() {
-  UpdateChecksum();
-}
-
-File::MemoryCheckingScopedFD::MemoryCheckingScopedFD(int fd) : file_(fd) {
-  UpdateChecksum();
-}
-
-File::MemoryCheckingScopedFD::~MemoryCheckingScopedFD() {}
-
-// static
-void File::MemoryCheckingScopedFD::ComputeMemoryChecksum(
-    unsigned int* out_checksum) const {
-  // Use a single iteration of a linear congruentional generator (lcg) to
-  // provide a cheap checksum unlikely to be accidentally matched by a random
-  // memory corruption.
-
-  // By choosing constants that satisfy the Hull-Duebell Theorem on lcg cycle
-  // length, we insure that each distinct fd value maps to a distinct checksum,
-  // which maximises the utility of our checksum.
-
-  // This code uses "unsigned int" throughout for its defined modular semantics,
-  // which implicitly gives us a divisor that is a power of two.
-
-  const unsigned int kMultiplier = 13035 * 4 + 1;
-  COMPILE_ASSERT(((kMultiplier - 1) & 3) == 0, pred_must_be_multiple_of_four);
-  const unsigned int kIncrement = 1595649551;
-  COMPILE_ASSERT(kIncrement & 1, must_be_coprime_to_powers_of_two);
-
-  *out_checksum =
-      static_cast<unsigned int>(file_.get()) * kMultiplier + kIncrement;
-}
-
-void File::MemoryCheckingScopedFD::Check() const {
-  unsigned int computed_checksum;
-  ComputeMemoryChecksum(&computed_checksum);
-  CHECK_EQ(file_memory_checksum_, computed_checksum) << "corrupted fd memory";
-}
-
-void File::MemoryCheckingScopedFD::UpdateChecksum() {
-  ComputeMemoryChecksum(&file_memory_checksum_);
-}
-
 // NaCl doesn't implement system calls to open files directly.
 #if !defined(OS_NACL)
 // TODO(erikkay): does it make sense to support FLAG_EXCLUSIVE_* here?