Add float version of gfx::Range

ui/gfx/render_text_unittest.cc

Index: ui/gfx/render_text_unittest.cc
diff --git a/ui/gfx/render_text_unittest.cc b/ui/gfx/render_text_unittest.cc
index 03425aa2b38c4daeadeb576480d48a9242eddd5d..a77cbc575cb42fc5c551bd12f58cea5aec9f9f8c 100644
--- a/ui/gfx/render_text_unittest.cc
+++ b/ui/gfx/render_text_unittest.cc
@@ -2161,7 +2161,7 @@ TEST_F(RenderTextTest, HarfBuzz_SubglyphGraphemeCases) {
     auto first_grapheme_bounds = run->GetGraphemeBounds(iter, 0);
     EXPECT_EQ(first_grapheme_bounds, run->GetGraphemeBounds(iter, 1));
     auto second_grapheme_bounds = run->GetGraphemeBounds(iter, 2);
-    EXPECT_EQ(first_grapheme_bounds.second, second_grapheme_bounds.first);
+    EXPECT_EQ(first_grapheme_bounds.end(), second_grapheme_bounds.start());
   }
 }