Replace uses of hash_map in //base

base/trace_event/heap_profiler_allocation_context.h

 // 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.
 
 #ifndef BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_
 #define BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
+#include <functional>
+
 #include "base/base_export.h"
-#include "base/containers/hash_tables.h"
 
 namespace base {
 namespace trace_event {
 
 // When heap profiling is enabled, tracing keeps track of the allocation
 // context for each allocation intercepted. It is generated by the
 // |AllocationContextTracker| which keeps stacks of context in TLS.
 // The tracker is initialized lazily.
 
 // The backtrace in the allocation context is a snapshot of the stack. For now,
@@ skipping 79 matching lines @@
 
 // Struct to store the size and count of the allocations.
 struct AllocationMetrics {
   size_t size;
   size_t count;
 };
 
 }  // namespace trace_event
 }  // namespace base
 
-namespace BASE_HASH_NAMESPACE {
+namespace std {
 
 template <>
 struct BASE_EXPORT hash<base::trace_event::StackFrame> {
   size_t operator()(const base::trace_event::StackFrame& frame) const;
 };
 
 template <>
 struct BASE_EXPORT hash<base::trace_event::Backtrace> {
   size_t operator()(const base::trace_event::Backtrace& backtrace) const;
 };
 
 template <>
 struct BASE_EXPORT hash<base::trace_event::AllocationContext> {
   size_t operator()(const base::trace_event::AllocationContext& context) const;
 };
 
-}  // BASE_HASH_NAMESPACE
+}  // namespace std
 
 #endif  // BASE_TRACE_EVENT_HEAP_PROFILER_ALLOCATION_CONTEXT_H_