Comment 6 for bug 1575191

I can understand why google is changing the width based on the viewport height, there is some logic behind it...
They want the page to render in a way that prevents posts being vertically cropped too much (which would result in the user only being able to view a small part of the post and having to scroll back and forth to read it or missing the picture or whatever). The way they are doing this is by changing the width of the contech which scales the overall page on most mobile browsers.

It looks like the issue is when you scroll down the browser automatically hides the tab and location bar which then changes the viewport size which then triggers the page to rescale. This wont only happen on G+ this will happen on lost of sites. Sites don't expect the viewport size to change unless the browser is actually being resized.

I'm not sure what the correct solution is but I would say one potential (but perhaps not very clean solution) would be not to change the viewport size when the tab/location bar is hidden if its a website which requires a vertical scroll bar. Essentially pretend the viewport stays a constant size even though in reality it has got larger. Like I said this is not an ideal solution but chances are if you are on a website with a vertical scroll bar the exact height shouldn't be hugely relevant anyway.

The other option is as was mentioned to see how Android deals with it. The location bar in Chrome on Android DOES hide but interestingly enough only under certain circumstances. I noticed when looking at Google results it didn't hide until I first tried to scroll up beyond the limit.