ui: Fix removing a number from the SequentialIDGenerator.

Make sure when a number is released, the |min_available_slot_| is updated accordingly,
so that subsequent allocations are set correctly to the lowest available ID.

BUG=292929
R=sky@chromium.org

Review URL: https://codereview.chromium.org/23654045

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@223517 0039d316-1c4b-4281-b951-d872f2087c98

ui/base/sequential_id_generator.cc

@@ -40,7 +40,7 @@ uint32 SequentialIDGenerator::GetGeneratedID(uint32 number) {
   if (find != number_to_id_.end())
     return find->second;
 
-  int id = GetNextAvailableSlot();
+  int id = GetNextAvailableID();
   number_to_id_.insert(std::make_pair(number, id));
   id_to_number_.insert(std::make_pair(id, number));
   return id;
@@ -51,18 +51,17 @@ bool SequentialIDGenerator::HasGeneratedIDFor(uint32 number) const {
 }
 
 void SequentialIDGenerator::ReleaseGeneratedID(uint32 id) {
-  if (id < min_available_id_) {
-    min_available_id_ = id;
-    DCHECK_GE(min_available_id_, min_id_);
-  }
+  UpdateNextAvailableIDAfterRelease(id);
   Remove(id, &id_to_number_, &number_to_id_);
 }
 
 void SequentialIDGenerator::ReleaseNumber(uint32 number) {
+  DCHECK_GT(number_to_id_.count(number), 0U);
+  UpdateNextAvailableIDAfterRelease(number_to_id_[number]);
   Remove(number, &number_to_id_, &id_to_number_);
 }
 
-uint32 SequentialIDGenerator::GetNextAvailableSlot() {
+uint32 SequentialIDGenerator::GetNextAvailableID() {
   const uint32 kMaxID = 128;
   while (id_to_number_.count(min_available_id_) > 0 &&
          min_available_id_ < kMaxID) {
@@ -73,4 +72,11 @@ uint32 SequentialIDGenerator::GetNextAvailableSlot() {
   return min_available_id_;
 }
 
+void SequentialIDGenerator::UpdateNextAvailableIDAfterRelease(uint32 id) {
+  if (id < min_available_id_) {
+    min_available_id_ = id;
+    DCHECK_GE(min_available_id_, min_id_);
+  }
+}
+
 }  // namespace ui

ui/base/sequential_id_generator.h

@@ -42,7 +42,9 @@ class UI_EXPORT SequentialIDGenerator {
  private:
   typedef base::hash_map<uint32, uint32> IDMap;
 
-  uint32 GetNextAvailableSlot();
+  uint32 GetNextAvailableID();
+
+  void UpdateNextAvailableIDAfterRelease(uint32 id);
 
   IDMap number_to_id_;
   IDMap id_to_number_;

ui/base/sequential_id_generator_unittest.cc

@@ -38,4 +38,25 @@ TEST(SequentialIDGeneratorTest, AddRemove) {
   EXPECT_FALSE(generator.HasGeneratedIDFor(45));
 }
 
+TEST(SequentialIDGeneratorTest, RemoveMultipleNumbers) {
+  const uint32 kMinID = 4;
+  SequentialIDGenerator generator(kMinID);
+
+  EXPECT_EQ(4U, generator.GetGeneratedID(45));
+  EXPECT_EQ(5U, generator.GetGeneratedID(55));
+  EXPECT_EQ(6U, generator.GetGeneratedID(15));
+
+  generator.ReleaseNumber(45);
+  EXPECT_FALSE(generator.HasGeneratedIDFor(45));
+  generator.ReleaseNumber(15);
+  EXPECT_FALSE(generator.HasGeneratedIDFor(15));
+
+  EXPECT_EQ(5U, generator.GetGeneratedID(55));
+  EXPECT_EQ(4U, generator.GetGeneratedID(12));
+
+  generator.ReleaseNumber(12);
+  generator.ReleaseNumber(55);
+  EXPECT_EQ(4U, generator.GetGeneratedID(0));
+}
+
 }  // namespace ui