Make flat containers stable, allow constructing from vector.

base/containers/flat_map_unittest.cc

Index: base/containers/flat_map_unittest.cc
diff --git a/base/containers/flat_map_unittest.cc b/base/containers/flat_map_unittest.cc
index 18524efb6c70a78844bc5acc1c14cea6d0eaa349..0556527635a69ebe16153cd33134fdefc8e96fe6 100644
--- a/base/containers/flat_map_unittest.cc
+++ b/base/containers/flat_map_unittest.cc
@@ -36,10 +36,16 @@ TEST(FlatMap, IncompleteType) {
 
 TEST(FlatMap, RangeConstructor) {
   flat_map<int, int>::value_type input_vals[] = {
-      {1, 1}, {1, 1}, {1, 1}, {2, 2}, {2, 2}, {2, 2}, {3, 3}, {3, 3}, {3, 3}};
+      {1, 1}, {1, 2}, {1, 3}, {2, 1}, {2, 2}, {2, 3}, {3, 1}, {3, 2}, {3, 3}};
 
-  flat_map<int, int> cont(std::begin(input_vals), std::end(input_vals));
-  EXPECT_THAT(cont, ElementsAre(std::make_pair(1, 1), std::make_pair(2, 2),
+  flat_map<int, int> first(std::begin(input_vals), std::end(input_vals),
+                           KEEP_FIRST_OF_DUPES);
+  EXPECT_THAT(first, ElementsAre(std::make_pair(1, 1), std::make_pair(2, 1),
+                                 std::make_pair(3, 1)));
+
+  flat_map<int, int> last(std::begin(input_vals), std::end(input_vals),
+                          KEEP_LAST_OF_DUPES);
+  EXPECT_THAT(last, ElementsAre(std::make_pair(1, 3), std::make_pair(2, 3),
                                 std::make_pair(3, 3)));
 }
 
@@ -60,13 +66,40 @@ TEST(FlatMap, MoveConstructor) {
   EXPECT_EQ(1U, moved.count(MoveOnlyInt(4)));
 }
 
+TEST(FlatMap, VectorConstructor) {
+  using IntPair = std::pair<int, int>;
+  using IntMap = flat_map<int, int>;
+  {
+    std::vector<IntPair> vect{{1, 1}, {1, 2}, {2, 1}};
+    IntMap map(std::move(vect), KEEP_FIRST_OF_DUPES);
+    EXPECT_THAT(map, ElementsAre(IntPair(1, 1), IntPair(2, 1)));
+  }
+  {
+    std::vector<IntPair> vect{{1, 1}, {1, 2}, {2, 1}};
+    IntMap map(std::move(vect), KEEP_LAST_OF_DUPES);
+    EXPECT_THAT(map, ElementsAre(IntPair(1, 2), IntPair(2, 1)));
+  }
+}
+
 TEST(FlatMap, InitializerListConstructor) {
-  flat_map<int, int> cont{{1, 1}, {2, 2}, {3, 3},   {4, 4},
-                          {5, 5}, {6, 6}, {10, 10}, {8, 8}};
-  EXPECT_THAT(cont, ElementsAre(std::make_pair(1, 1), std::make_pair(2, 2),
-                                std::make_pair(3, 3), std::make_pair(4, 4),
-                                std::make_pair(5, 5), std::make_pair(6, 6),
-                                std::make_pair(8, 8), std::make_pair(10, 10)));
+  {
+    flat_map<int, int> cont(
+        {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {1, 2}, {10, 10}, {8, 8}},
+        KEEP_FIRST_OF_DUPES);
+    EXPECT_THAT(cont, ElementsAre(std::make_pair(1, 1), std::make_pair(2, 2),
+                                  std::make_pair(3, 3), std::make_pair(4, 4),
+                                  std::make_pair(5, 5), std::make_pair(8, 8),
+                                  std::make_pair(10, 10)));
+  }
+  {
+    flat_map<int, int> cont(
+        {{1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {1, 2}, {10, 10}, {8, 8}},
+        KEEP_LAST_OF_DUPES);
+    EXPECT_THAT(cont, ElementsAre(std::make_pair(1, 2), std::make_pair(2, 2),
+                                  std::make_pair(3, 3), std::make_pair(4, 4),
+                                  std::make_pair(5, 5), std::make_pair(8, 8),
+                                  std::make_pair(10, 10)));
+  }
 }
 
 TEST(FlatMap, InsertFindSize) {