Frank, firstly you can't combine these two charts into one line chart the reason is one chart have max of 11 company names and other chart needs to show trend line for each company name.
In the second chart you don't have 2nd dimension as Company Name but you need to show trend line for each company name. So in the second chart add Company name as 2nd dimension.
If you want combine two charts, you may want slightly change the requirement like create calculated dimension like CompanyName - Top 10 or CompanyName - Not in Top 10.
Thanks for the info. I'll try modifying the second chart by adding the second dimension and see if this allows me to overlay the charts a bit easier. The idea for combining the charts by changing the requirements is less desirable, as the request was to show trending for the top 10 companies as it compared to overall trends.