I am taking this up.

In addition to utilize EphemeralRange in UpdateStartEnd(), we want to utilize
EphemeralRange in
- Create(Document& document, 
         const EditingStyle* style,
         const Position& start,
         const Position& end)
 and it's wrappers.
- ApplyStyleCommand(Document&,
                    const EditingStyle*,
                    const Position& start,
                    const Position& end);

  void RemoveInlineStyle(EditingStyle*,
                         const Position& start,
                         const Position& end,
                         EditingState*);

  void FixRangeAndApplyInlineStyle(EditingStyle*,
                                   const Position& start,
                                   const Position& end,
                                   EditingState*);

and more functions to take |Position start, Position end|.

We may want to use |range_| instead of |start_| and |end_|.
If we can use |EpehemralRange|, it is nice.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5eeed90f5c798b2b3294e19e7646a5c338aed517

commit 5eeed90f5c798b2b3294e19e7646a5c338aed517
Author: tanvir.rizvi <tanvir.rizvi@samsung.com>
Date: Tue Apr 03 11:18:14 2018

Make ApplyStyleCommand::UpdateStartEnd to take EphemeralRange

UpdateStartEnd takes start and end position as parameters,
and then does a DCHECK_LE for start and end.
EphemeralRange constructor also does same DCHECK.
Since UpdateStartEnd is called from many places,
so to catch a bug at the call site, function
UpdateStartEnd is made to take EphemeralRange
instead.

Bug: 826106
Change-Id: I6e1cd23e9aac2846a2f083cd6f4d8110fa3a9085
Reviewed-on: https://chromium-review.googlesource.com/989852
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Tanvir Rizvi <tanvir.rizvi@samsung.com>
Cr-Commit-Position: refs/heads/master@{#547668}
[modify] https://crrev.com/5eeed90f5c798b2b3294e19e7646a5c338aed517/third_party/WebKit/Source/core/editing/commands/ApplyStyleCommand.cpp
[modify] https://crrev.com/5eeed90f5c798b2b3294e19e7646a5c338aed517/third_party/WebKit/Source/core/editing/commands/ApplyStyleCommand.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f8554ddf85336ebf6b733022fa2b5fd23dc22065

commit f8554ddf85336ebf6b733022fa2b5fd23dc22065
Author: tanvir.rizvi <tanvir.rizvi@samsung.com>
Date: Tue Apr 10 09:16:59 2018

Use EphemeralRange in ApplyStyleCommand::RemoveInlineStyle

For code health we use Ephemeral range instead of
passsing position in RemoveInlineStyle.
With this we catch a bug at call sites,
as EphemeralRange construction takes care of the
current DCHECKS in RemoveInlineStyle

Bug: 826106
Change-Id: Ibaa37789f7671aa464b4c87d30f12bd023a67a3d
Reviewed-on: https://chromium-review.googlesource.com/1001437
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Tanvir Rizvi <tanvir.rizvi@samsung.com>
Cr-Commit-Position: refs/heads/master@{#549466}
[modify] https://crrev.com/f8554ddf85336ebf6b733022fa2b5fd23dc22065/third_party/blink/renderer/core/editing/commands/apply_style_command.cc
[modify] https://crrev.com/f8554ddf85336ebf6b733022fa2b5fd23dc22065/third_party/blink/renderer/core/editing/commands/apply_style_command.h