Created attachment 337061 [details]
Attached testcase is similar to attachment 312006 [details] but using subframes instead of "overflow: auto" nodes.
If you find "text" with the Find UI, the result will be highlighted in that order:
* Main frame: text5a, text5b, text5c, text10a text10b text10c
* Subframe 1: text1a, text1b, text1c, ... text4a, text4b, text4c
* Subframe 2: text6a, text6b, text6c, ... text9a text9b text9c
- The result from the main frame are returned first. Although this is different from "overflow: auto" node, it is the same behavior as on desktop and other browsers.
- Scrolling and smart magnification work for the main frame and the first subframe.
For the second subframe, text6a, text6b, text6c, ... text9a text9b text9c are highlighted as expected BUT the scrolling / magnification reveals the *first* subframe (you can scroll down to check that the expected text is highlighted).