Improve modules' TypeError exception messages.

Source/modules/indexeddb/IDBCursor.cpp

Index: Source/modules/indexeddb/IDBCursor.cpp
diff --git a/Source/modules/indexeddb/IDBCursor.cpp b/Source/modules/indexeddb/IDBCursor.cpp
index 8ea735858c5ba2e5254bbb7ca3ec2074d93d6faa..e7b30239821438070b2f744aff5ac65b29ba93bc 100644
--- a/Source/modules/indexeddb/IDBCursor.cpp
+++ b/Source/modules/indexeddb/IDBCursor.cpp
@@ -161,7 +161,7 @@ void IDBCursor::advance(unsigned long count, ExceptionState& exceptionState)
     }
 
     if (!count) {
-        exceptionState.throwUninformativeAndGenericTypeError();
+        exceptionState.throwTypeError("The count provided is 0.");
         return;
     }
 
@@ -392,7 +392,7 @@ IndexedDB::CursorDirection IDBCursor::stringToDirection(const String& directionS
     if (directionString == IDBCursor::directionPrevUnique())
         return IndexedDB::CursorPrevNoDuplicate;
 
-    exceptionState.throwUninformativeAndGenericTypeError();
+    exceptionState.throwTypeError("The direction provided ('" + directionString + "') is not one of 'next', 'nextunique', 'prev', or 'prevunique'.");
     return IndexedDB::CursorNext;
 }