Fix fast/writing-mode/text-combine-line-break.html on Mac

The test was actually passing on Mac, but a 1px difference caused the
test to report a failure on difference between -0 and 0.

The test started to fail after
https://chromium-review.googlesource.com/c/chromium/src/+/1614448 which
fixed some vertical-rl issues. Before that, the 1px difference was added
in a wrong direction and didn't trigger the -0 vs 0 issue.

Add + 1 - 1 to convert -0 to 0.

Bug: 968033
Change-Id: Idfd6c047f77193be571219459629c10439004de0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1648710Reviewed-by: Philip Rogers <pdr@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667158}

third_party/blink/web_tests/TestExpectations

@@ -2128,8 +2128,6 @@ crbug.com/658305 css3/filters/effect-reference-zoom.html [ Failure Pass ]
 crbug.com/658305 css3/filters/effect-reference-zoom-hw.html [ Failure Pass ]
 crbug.com/658305 css3/filters/filter-effect-removed.html [ Failure Pass ]
 
-crbug.com/968033 [ Mac ] fast/writing-mode/text-combine-line-break.html [ Failure ]
-
 crbug.com/524160 [ Debug ] http/tests/media/media-source/stream_memory_tests/mediasource-appendbuffer-quota-exceeded-default-buffers.html [ Timeout ]
 
 # Run the tests with the default MSE buffer sizes in the main test suite and the tests for 1MB buffers set via command line in a virtual test suite

third_party/blink/web_tests/fast/writing-mode/text-combine-line-break.html

@@ -48,7 +48,8 @@
         var block = element.parentElement.getBoundingClientRect()
         var column = rect.top - block.top;
         var row = block.right - rect.right;
-        return [Math.round(column / 20), Math.round(row / 20)];
+        // "+ 1 - 1" is to convert -0 to 0.
+        return [Math.round(column / 20) + 1 - 1, Math.round(row / 20) + 1 - 1];
     }
 })();