Distinguish null IDBKey (no value) and invalid IDBKey (value is not valid key)

content/common/indexed_db/indexed_db_key.cc

Index: content/common/indexed_db/indexed_db_key.cc
diff --git a/content/common/indexed_db/indexed_db_key.cc b/content/common/indexed_db/indexed_db_key.cc
index 1b9491d7b87c98f60ef3b8f39f966638a1efce9f..f2a7cfbb7930b12f47237a7f50d692f925077da6 100644
--- a/content/common/indexed_db/indexed_db_key.cc
+++ b/content/common/indexed_db/indexed_db_key.cc
@@ -11,7 +11,7 @@
 using WebKit::WebIDBKey;
 
 IndexedDBKey::IndexedDBKey()
-    : type_(WebIDBKey::InvalidType),
+    : type_(WebIDBKey::NullType),
       date_(0),
       number_(0) {
 }
@@ -27,6 +27,10 @@ void IndexedDBKey::SetInvalid() {
   type_ = WebIDBKey::InvalidType;
 }
 
+void IndexedDBKey::SetNull() {
+  type_ = WebIDBKey::NullType;
+}
+
 void IndexedDBKey::SetArray(const std::vector<IndexedDBKey>& array) {
   type_ = WebIDBKey::ArrayType;
   array_ = array;
@@ -72,10 +76,9 @@ IndexedDBKey::operator WebIDBKey() const {
     case WebIDBKey::NumberType:
       return WebIDBKey::createNumber(number_);
     case WebIDBKey::InvalidType:
-    default:
-      // TODO(jsbell): Remove "default" label once WebKit bug 76487 has rolled.
-      // http://crbug.com/110956
       return WebIDBKey::createInvalid();
+    case WebIDBKey::NullType:
+      return WebIDBKey::createNull();
   }
   NOTREACHED();
   return WebIDBKey::createInvalid();