Align base::hash_map with C++11.

base/containers/small_map_unittest.cc

Index: base/containers/small_map_unittest.cc
diff --git a/base/containers/small_map_unittest.cc b/base/containers/small_map_unittest.cc
index bc76e370397b40053db342fa7e84000599a6b2b4..f87a8f09cbf5fcc75ffa338ba48fb549f2449f22 100644
--- a/base/containers/small_map_unittest.cc
+++ b/base/containers/small_map_unittest.cc
@@ -414,9 +414,8 @@ namespace {
 
 class hash_map_add_item : public hash_map<int, int> {
  public:
-  hash_map_add_item() : hash_map<int, int>() {}

[davidben, 2014/10/02 22:38:50]

This is to work around an incredibly annoying problem with type aliases. If we
were to call it base::unordered_map, I think we would avoid this problem.

The trouble is that we're subclassing base::hash_map<int, int>. But within
base::hash_map, 'hash_map' is bound to std::hash_map. And so inside the
subclass, we inherit the parent class's binding of 'hash_map' over the one in
base. I believe this is similar why this works:

  namespace a {
  struct Foo {};
  }
  struct Bar : public a::Foo {
    Bar() : Foo() {}
  };

And this:

  namespace a {
  struct Foo {};
  typedef Foo Foo2;
  }
  struct Bar : public a::Foo2 {
    Bar() : Foo() {}
  };

But not this:

  namespace a {
  struct Foo {};
  typedef Foo Foo2;
  }
  struct Bar : public a::Foo2 {
    Bar() : Foo2() {}
  };


I'm going to leave it as-is for now since subclassing hash_map is a bizarre
thing to do, but we may want do the rename now to avoid this.

-  explicit hash_map_add_item(const std::pair<int, int>& item)
-      : hash_map<int, int>() {
+  hash_map_add_item() {}
+  explicit hash_map_add_item(const std::pair<int, int>& item) {
     insert(item);
   }
 };