Improve handling of failed integer type conversions.

Source/modules/indexeddb/IDBCursor.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 124 matching lines @@
             return 0;
         }
     }
 
     return objectStore->put(WebIDBDatabase::CursorUpdate, IDBAny::create(this), state, value, m_primaryKey, exceptionState);
 }
 
 void IDBCursor::advance(unsigned long count, ExceptionState& exceptionState)
 {
     IDB_TRACE("IDBCursor::advance");
+    if (!count) {

[jsbell, 2014/01/02 18:03:23]

Any particular reason for changing the order? lgtm anyway, since this case is
listed first in the spec (even though we couldn't get consensus on a strict
ordering in the spec).

[sof, 2014/01/02 19:30:31]

The spec was the motivation for moving it up, but also that it makes logical
sense to have it first -- to my mind, the >0 constraint being an extension of
[EnforceRange] validation of the argument. Hence having other observable
exceptions between these two parts would be unnatural.

But that's all API implementation machinery details -- if it is preferable to
keep it the way it was, happy to revert the placement.

+        exceptionState.throwTypeError("A count argument with value 0 (zero) was supplied, must be greater than 0.");
+        return;
+    }
     if (!m_gotValue) {
         exceptionState.throwDOMException(InvalidStateError, IDBDatabase::noValueErrorMessage);
         return;
     }
     if (isDeleted()) {
         exceptionState.throwDOMException(InvalidStateError, IDBDatabase::sourceDeletedErrorMessage);
         return;
     }
 
     if (m_transaction->isFinished()) {
         exceptionState.throwDOMException(TransactionInactiveError, IDBDatabase::transactionFinishedErrorMessage);
         return;
     }
     if (!m_transaction->isActive()) {
         exceptionState.throwDOMException(TransactionInactiveError, IDBDatabase::transactionInactiveErrorMessage);
         return;
     }
 
-    if (!count) {
-        exceptionState.throwUninformativeAndGenericTypeError();
-        return;
-    }
-
     m_request->setPendingCursor(this);
     m_gotValue = false;
     m_backend->advance(count, WebIDBCallbacksImpl::create(m_request).leakPtr());
 }
 
 void IDBCursor::continueFunction(ExecutionContext* context, const ScriptValue& keyValue, ExceptionState& exceptionState)
 {
     IDB_TRACE("IDBCursor::continue");
     DOMRequestState requestState(context);
     RefPtr<IDBKey> key = keyValue.isUndefined() || keyValue.isNull() ? 0 : scriptValueToIDBKey(&requestState, keyValue);
@@ skipping 233 matching lines @@
     case IndexedDB::CursorPrevNoDuplicate:
         return IDBCursor::directionPrevUnique();
 
     default:
         ASSERT_NOT_REACHED();
         return IDBCursor::directionNext();
     }
 }
 
 } // namespace WebCore