Replace uses of hash_map in //base

base/trace_event/heap_profiler_allocation_context.cc

 // Copyright 2015 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 "base/trace_event/heap_profiler_allocation_context.h"
 
 #include <cstring>
 
 #include "base/hash.h"
 #include "base/macros.h"
@@ skipping 30 matching lines @@
                                      const char* type_name)
   : backtrace(backtrace), type_name(type_name) {}
 
 bool operator==(const AllocationContext& lhs, const AllocationContext& rhs) {
   return (lhs.backtrace == rhs.backtrace) && (lhs.type_name == rhs.type_name);
 }
 
 bool operator!=(const AllocationContext& lhs, const AllocationContext& rhs) {
   return !(lhs == rhs);
 }
+
 }  // namespace trace_event
 }  // namespace base
 
-namespace BASE_HASH_NAMESPACE {
+namespace std {
+
 using base::trace_event::AllocationContext;
 using base::trace_event::Backtrace;
 using base::trace_event::StackFrame;
 
 size_t hash<StackFrame>::operator()(const StackFrame& frame) const {
   return hash<const void*>()(frame.value);
 }
 
 size_t hash<Backtrace>::operator()(const Backtrace& backtrace) const {
   const void* values[Backtrace::kMaxFrameCount];
@@ skipping 13 matching lines @@
   // will still redistribute keys bijectively on 64-bit architectures because
   // the magic number is coprime to 2^64.
   size_t type_hash = reinterpret_cast<size_t>(ctx.type_name) * 2654435761;
 
   // Multiply one side to break the commutativity of +. Multiplication with a
   // number coprime to |numeric_limits<size_t>::max() + 1| is bijective so
   // randomness is preserved.
   return (backtrace_hash * 3) + type_hash;
 }
 
-}  // BASE_HASH_NAMESPACE
+}  // namespace std