Copying c#10 from  issue 650120 


Value of: GetSelectionBoundsUnion()
  Actual: 0,491 3x17
Expected: expected_line_bounds
Which is: 0,491 3x18


I think this is caused by the following:

- for calculating expected_line_bounds in test, std::ceil is used for both, width and height

https://cs.chromium.org/chromium/src/ui/gfx/render_text_unittest.cc?l=4253

const Size line_size(std::ceil(line.size.width()),
                         std::ceil(line.size.height()));

dbg info:
line.size.height(): 17,760000, ceil(line.size.height()): 18,000000


- but in RenderTextHarfBuzz::GetSubstringBounds() function, std::ceil is used only for width

https://cs.chromium.org/chromium/src/ui/gfx/render_text_harfbuzz.cc?l=1111

int end_x = std::ceil(x + width);
int start_x = std::ceil(x);
gfx::Rect rect(start_x, 0, end_x - start_x, line.size.height());

dbg info:
line.size.height() : 17,760000
rect.height(): 17