Revert of Allow std::unordered_*.

base/hash.h

Index: base/hash.h
diff --git a/base/hash.h b/base/hash.h
index d5dc5499de522de7a10fd213290ba80739ae6eef..ed8d9fd4cc9b987272f9d54ffa854c2d86f7129e 100644
--- a/base/hash.h
+++ b/base/hash.h
@@ -10,7 +10,6 @@
 
 #include <limits>
 #include <string>
-#include <utility>
 
 #include "base/base_export.h"
 #include "base/logging.h"
@@ -36,86 +35,6 @@
   return Hash(str.data(), str.size());
 }
 
-// Implement hashing for pairs of at-most 32 bit integer values.
-// When size_t is 32 bits, we turn the 64-bit hash code into 32 bits by using
-// multiply-add hashing. This algorithm, as described in
-// Theorem 4.3.3 of the thesis "Über die Komplexität der Multiplikation in
-// eingeschränkten Branchingprogrammmodellen" by Woelfel, is:
-//
-//   h32(x32, y32) = (h64(x32, y32) * rand_odd64 + rand16 * 2^16) % 2^64 / 2^32
-//
-// Contact danakj@chromium.org for any questions.
-inline size_t HashInts32(uint32_t value1, uint32_t value2) {
-  uint64_t value1_64 = value1;
-  uint64_t hash64 = (value1_64 << 32) | value2;
-
-  if (sizeof(size_t) >= sizeof(uint64_t))
-    return static_cast<size_t>(hash64);
-
-  uint64_t odd_random = 481046412LL << 32 | 1025306955LL;
-  uint32_t shift_random = 10121U << 16;
-
-  hash64 = hash64 * odd_random + shift_random;
-  size_t high_bits = static_cast<size_t>(
-      hash64 >> (8 * (sizeof(uint64_t) - sizeof(size_t))));
-  return high_bits;
-}
-
-// Implement hashing for pairs of up-to 64-bit integer values.
-// We use the compound integer hash method to produce a 64-bit hash code, by
-// breaking the two 64-bit inputs into 4 32-bit values:
-// http://opendatastructures.org/versions/edition-0.1d/ods-java/node33.html#SECTION00832000000000000000
-// Then we reduce our result to 32 bits if required, similar to above.
-inline size_t HashInts64(uint64_t value1, uint64_t value2) {
-  uint32_t short_random1 = 842304669U;
-  uint32_t short_random2 = 619063811U;
-  uint32_t short_random3 = 937041849U;
-  uint32_t short_random4 = 3309708029U;
-
-  uint32_t value1a = static_cast<uint32_t>(value1 & 0xffffffff);
-  uint32_t value1b = static_cast<uint32_t>((value1 >> 32) & 0xffffffff);
-  uint32_t value2a = static_cast<uint32_t>(value2 & 0xffffffff);
-  uint32_t value2b = static_cast<uint32_t>((value2 >> 32) & 0xffffffff);
-
-  uint64_t product1 = static_cast<uint64_t>(value1a) * short_random1;
-  uint64_t product2 = static_cast<uint64_t>(value1b) * short_random2;
-  uint64_t product3 = static_cast<uint64_t>(value2a) * short_random3;
-  uint64_t product4 = static_cast<uint64_t>(value2b) * short_random4;
-
-  uint64_t hash64 = product1 + product2 + product3 + product4;
-
-  if (sizeof(size_t) >= sizeof(uint64_t))
-    return static_cast<size_t>(hash64);
-
-  uint64_t odd_random = 1578233944LL << 32 | 194370989LL;
-  uint32_t shift_random = 20591U << 16;
-
-  hash64 = hash64 * odd_random + shift_random;
-  size_t high_bits = static_cast<size_t>(
-      hash64 >> (8 * (sizeof(uint64_t) - sizeof(size_t))));
-  return high_bits;
-}
-
-template<typename T1, typename T2>
-inline size_t HashInts(T1 value1, T2 value2) {
-  // This condition is expected to be compile-time evaluated and optimised away
-  // in release builds.
-  if (sizeof(T1) > sizeof(uint32_t) || (sizeof(T2) > sizeof(uint32_t)))
-    return HashInts64(value1, value2);
-
-  return HashInts32(value1, value2);
-}
-
-// A templated hasher for pairs of integer types.
-template<typename T> struct IntPairHash;
-
-template<typename Type1, typename Type2>
-struct IntPairHash<std::pair<Type1, Type2>> {
-  size_t operator()(std::pair<Type1, Type2> value) const {
-    return HashInts(value.first, value.second);
-  }
-};
-
 }  // namespace base
 
 #endif  // BASE_HASH_H_