Rewrite ElideText unittests

This CL is rewriting the ElideText unittests.
The goal of this rewrite is to allow adding more unittests.
  * ELIDE_HEAD
  * ELIDE_EMAIL
  * ELIDE_MIDDLE
  * Eliding with styles

It is now using a templated tests to ease debugging.

A change to the way glyph_width_for_test_ work was needed.
Zero width codepoints will stay zero width, even if a
glyph width is provided. This is required to ensures
RLM and LRM (directional marker) stay with width zero.
Otherwise a DCHECK is failing since the text can be larger
with eliding (2 glyphs instead of 1 glyph).

Bug: 1025561
Change-Id: I19f18fb99f52edbbb59d170f7b47bef3a3f3de5f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1975056
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726406}

ui/gfx/render_text_harfbuzz.cc

@@ -1337,10 +1337,13 @@ void ShapeRunWithFont(const ShapeRunWithFontInput& in,
     const SkScalar y_offset =
         HarfBuzzUnitsToSkiaScalar(hb_positions[i].y_offset);
     out->positions[i].set(out->width + x_offset, -y_offset);
-    out->width += (in.glyph_width_for_test > 0)
-                      ? in.glyph_width_for_test
-                      : HarfBuzzUnitsToFloat(hb_positions[i].x_advance) +
-                            in.glyph_spacing;
+
+    if (in.glyph_width_for_test == 0)
+      out->width +=
+          HarfBuzzUnitsToFloat(hb_positions[i].x_advance) + in.glyph_spacing;
+    else if (hb_positions[i].x_advance)  // Leave zero-width glyphs alone.
+      out->width += in.glyph_width_for_test;
+
     // Round run widths if subpixel positioning is off to match native behavior.
     if (!in.render_params.subpixel_positioning)
       out->width = std::round(out->width);