Inserting new code above existing code temporarily shifts adorners

``` csharp
int x = 5;  [x | 5]
```

``` csharp
int y = 2   [x | 5]
int x = 5;
```

Once you add the = 2, Roslyn sees the line as a 'valid' variable declarator, despite the lack of semicolon. Since it won't actually compile, it won't get executed and therefore there's a disparity between current and last executed operation IDs.
