• VSCode Version: 1.21.0 Insiders
• OS Version: Windows

Steps to Reproduce:

1. Install the C++ extension.
2. Use code like

int main()
{
#ifdef foo
text should appear gray here
#endif
}

3. Select the entire main method and start typing something else.

Bug: The new code is gray even though the lines are deleted. VS code appears to not handle the case where decorations are set on lines but the lines are removed. Our code eventually sends new text decorations but it takes a while to process.