I think I need to use this to access the file from my C# code:
Below is something that I think resembles what should be done:
I added to my AssemblyInfo.cs:
[assembly: System.Web.UI.WebResource("ReportingMDMWebPart.Height100Percent.js", "text/js", PerformSubstitution = true)]
My Height100Percent.js file is a duplicate of file on this page: Story of a mischievous Page Viewer Web Part.