I found the answer to my question regarding Canadian social benefits ie CPP, OAS. Here are IRS instructions for line 1a of form 1116:
"Lines 1a and 1b—Foreign Gross Income
Include income in the category checked above Part I that is taxable by the United States and is from sources within the country entered on line 1. You must include income even if it isn't taxable by that foreign country. "
This surely applies to CPP and OAS.
Also, note that line 3e includes the full amount of CPP and OAS from line 6a of form 1040 not the taxable amount of line 6b. Therefore it makes sense that the gross foreign income on form 1116 line 1a should also include CPP and OAS when figuring the ratio on line 3 f.
As the Turbotax step-by-step instructions say in "Other Gross Income", enter "any other gross income received from sources in Canada".
This is where to enter CPP and OAS plus other income. The total entered here will show up on 1116 line 1a. In the step-by-step process, I usually just total all these up and enter the total on one line with an abbreviated description as there are not enough boxes to enter all my items. I put the details in attached notes
