Switch base::IDMap to use unique_ptr.

base/id_map.h

Index: base/id_map.h
diff --git a/base/id_map.h b/base/id_map.h
index c0976b0557d9d15a5e51e8eae5b31afc7fd0f733..a252440c8c1f79ecbabea10642b9e02104d40cd7 100644
--- a/base/id_map.h
+++ b/base/id_map.h
@@ -7,7 +7,10 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <memory>
 #include <set>
+#include <type_traits>
+#include <utility>
 
 #include "base/containers/hash_tables.h"
 #include "base/logging.h"
@@ -40,7 +43,10 @@ class IDMap {
   using KeyType = K;
 
  private:
-  typedef base::hash_map<KeyType, T*> HashTable;
+  typedef typename std::conditional<OS == IDMapExternalPointer,

[danakj, 2016/09/15 20:08:40]

can you change these both to "using" instead of typedef

[aelias_OOO_until_Jul13, 2016/09/15 21:09:35]

Done.

+                                  T*,
+                                  std::unique_ptr<T>>::type V;
+  typedef base::hash_map<KeyType, V> HashTable;
 
  public:
   IDMap() : iteration_depth_(0), next_id_(1), check_on_null_data_(false) {
@@ -56,7 +62,6 @@ class IDMap {
     // thread. However, all the accesses may take place on another thread (or
     // sequence), such as the IO thread. Detaching again to clean this up.
     sequence_checker_.DetachFromSequence();
-    Releaser<OS, 0>::release_all(&data_);
   }
 
   // Sets whether Add and Replace should DCHECK if passed in NULL data.
@@ -69,7 +74,7 @@ class IDMap {
     DCHECK(!check_on_null_data_ || data);
     KeyType this_id = next_id_;
     DCHECK(data_.find(this_id) == data_.end()) << "Inserting duplicate item";
-    data_[this_id] = data;
+    data_[this_id] = V(data);
     next_id_++;
     return this_id;
   }
@@ -82,7 +87,7 @@ class IDMap {
     DCHECK(sequence_checker_.CalledOnValidSequence());
     DCHECK(!check_on_null_data_ || data);
     DCHECK(data_.find(id) == data_.end()) << "Inserting duplicate item";
-    data_[id] = data;
+    data_[id] = V(data);
   }
 
   void Remove(KeyType id) {
@@ -94,36 +99,29 @@ class IDMap {
     }
 
     if (iteration_depth_ == 0) {
-      Releaser<OS, 0>::release(i->second);
       data_.erase(i);
     } else {
       removed_ids_.insert(id);
     }
   }
 
-  // Replaces the value for |id| with |new_data| and returns a pointer to the
-  // existing value. If there is no entry for |id|, the map is not altered and
-  // nullptr is returned. The OwnershipSemantics of the map have no effect on
-  // how the existing value is treated, the IDMap does not delete the existing
-  // value being replaced.
-  T* Replace(KeyType id, T* new_data) {
+  // Replaces the value for |id| with |new_data| and returns the existing value
+  // (as a unique_ptr<> if in IDMapOwnPointer mode).  Should only be called with
+  // an already added id.
+  V Replace(KeyType id, V new_data) {
     DCHECK(sequence_checker_.CalledOnValidSequence());
     DCHECK(!check_on_null_data_ || new_data);
     typename HashTable::iterator i = data_.find(id);
-    if (i == data_.end()) {
-      NOTREACHED() << "Attempting to replace an item not in the list";
-      return nullptr;
-    }
+    DCHECK(i != data_.end());
 
-    T* temp = i->second;
-    i->second = new_data;
-    return temp;
+    std::swap(i->second, new_data);
+    return new_data;
   }
 
   void Clear() {
     DCHECK(sequence_checker_.CalledOnValidSequence());
     if (iteration_depth_ == 0) {
-      Releaser<OS, 0>::release_all(&data_);
+      data_.clear();
     } else {
       for (typename HashTable::iterator i = data_.begin();
            i != data_.end(); ++i)
@@ -140,8 +138,8 @@ class IDMap {
     DCHECK(sequence_checker_.CalledOnValidSequence());
     typename HashTable::const_iterator i = data_.find(id);
     if (i == data_.end())
-      return NULL;
-    return i->second;
+      return nullptr;
+    return &*i->second;
   }
 
   size_t size() const {
@@ -202,7 +200,7 @@ class IDMap {
 
     ReturnType* GetCurrentValue() const {
       DCHECK(map_->sequence_checker_.CalledOnValidSequence());
-      return iter_->second;
+      return &*iter_->second;
     }
 
     void Advance() {
@@ -234,25 +232,6 @@ class IDMap {
   typedef Iterator<const T> const_iterator;
 
  private:
-
-  // The dummy parameter is there because C++ standard does not allow
-  // explicitly specialized templates inside classes
-  template<IDMapOwnershipSemantics OI, int dummy> struct Releaser {
-    static inline void release(T* ptr) {}
-    static inline void release_all(HashTable* table) {}
-  };
-
-  template<int dummy> struct Releaser<IDMapOwnPointer, dummy> {
-    static inline void release(T* ptr) { delete ptr;}
-    static inline void release_all(HashTable* table) {
-      for (typename HashTable::iterator i = table->begin();
-           i != table->end(); ++i) {
-        delete i->second;
-      }
-      table->clear();
-    }
-  };
-
   void Compact() {
     DCHECK_EQ(0, iteration_depth_);
     for (const auto& i : removed_ids_)