Fix text rendering with RenderTextMac.

BUG=606705

Glyph 65535 means that the glyph is not printable.
Replacing it with 0 results in a striped glyph that's
rendered instead of non-printable glyphs.
Just remove old invalid code to fix this.
In my testing no Skia asserts were triggered.

Without this fix the title in tab of url :
https://www.google.ru/trends/yis/2016/RU?autoplay=1
will be incorrect rendered:
See https://bugs.chromium.org/p/chromium/issues/detail?id=606705#c4

Review-Url: https://codereview.chromium.org/2756683002
Cr-Commit-Position: refs/heads/master@{#457472}

ui/gfx/render_text_mac.mm

@@ -428,14 +428,6 @@ void RenderTextMac::ComputeRuns() {
     run->width = run_width;
     run->glyphs.resize(glyph_count);
     CTRunGetGlyphs(ct_run, empty_cf_range, &run->glyphs[0]);
-    // CTRunGetGlyphs() sometimes returns glyphs with value 65535 and zero
-    // width (this has been observed at the beginning of a string containing
-    // Arabic content). Passing these to Skia will trigger an assertion;
-    // instead set their values to 0.
-    for (size_t glyph = 0; glyph < glyph_count; glyph++) {
-      if (run->glyphs[glyph] == 65535)
-        run->glyphs[glyph] = 0;
-    }
 
     run->glyph_positions.resize(glyph_count);
     const CGPoint* positions_ptr = CTRunGetPositionsPtr(ct_run);