What does the yellow progress bar in stock browser means, while rendering downloading web page?
I've never seen it come from the right, nor have I seen it "gap", but the progress bar is just that, it shows the download progress for the page that you about to view.

After you posted your screenshot and video, it looks like that the browser is seeing that you are on the Malaysian version of Google. If I am correct, the Malaysian is read from Right to Left, which would be why the progress bar loads from right to left. 

If you just go to Google.com, it will load from left to right, or you have the default language on your device to be Malaysian, in which case, would default it to right to left.