Fixes RenderViewContextMenu override compilation.

Removed unnecessary spellcheck/os build flags checks.

The flag was causing the include not to happen due to a this change:

https://chromium.googlesource.com/chromium/src/+/de74ce301c50fd3a4815faff207c9592416eb337

commit de74ce301c50fd3a4815faff207c9592416eb337
Author: Siye Liu <siliu@microsoft.com>
Date:   Thu Jun 20 20:44:43 2019 +0000

    windows spellchecker integration.

    This CL aims to implement windows spellchecker integration in Chromium
    project, so that user can switch to use windows spellchecker or
    hunspell spellchecker at run time. We need to implement platform
    agnostic interfaces to integrate windows spellchecker into Chromium. We
    also need to refactor some code to enable runtime switch between
    Windows spellchecker and hunspell spellchecker.

    We have outlines following steps to achieve the goal:

    (1) Implement spellcheck_platform interface.
          spellcheck_platform is an interface that platform-specific
          spellchecker needs to implement. Create spellcheck_platform_win.cc
          which contains Windows specific logic. All COM calls are happeninn
          on the background thread. spellcheck_platform API are all async.

    (2) Refactor SpellCheckHostChromeImpl.
          SpellCheckHostChromeImpl is a derived class from SpellCheckHost
          which provides basic spellcheck support. Mac has separate
          implementation located at spell_check_host_chrome_impl_mac.cc.
          Windows can share the same implementation, therefore, I move the
          code to the base derived class at spellcheck_host_chrome_impl.cc
          and delete mac specific file.

    (3) Refactor SpellingRequest.
          SpellingRequest is owned by SpellCheckHostChromeImpl and is
          currently located at spell_check_host_chrome_impl_mac.cc file.
          Created seperate files spelling_request.h and spelling_request.cc
          for defination and declaration of SpellingRequest.

    (4) Refactor CreateNativeSpellingEngine().
          CreateNativeSpellingEngine() used to live in seperate files for
          different spellcheckers. For platform specific spellchecker, it
          is located at platform_spelling_engine.cc. For hunspell
          spellchecker, it is located at hunspell_engine.cc. In order to
          enable runtime switch between those two spellcheck services, We
          need to have a uniformed definiation. Therefore, I create a new
          fine spelling_engine.cc base class and put a uniformed defination
          of CreateNativeSpellingEngine().

    (5) Define USE_RENDERER_SPELLCHECKER build flag
          We already have USE_BROWSER_SPELLCHECKER build flag. The decision
          to use platform specific spellcheck or hunspell spellcheck is
          made at build time. It's not the case anymore. We want to switch
          between spellcheck services at runtime. use browser spellcheck
          (platform specific spellcheck) and use renderer spellcheck
          (hunspll spellcheck) are no longer mutually exclusive. I created
          USE_RENDERER_SPELLCHECKER build flag to indicate usage of
          hunspell spellcheck service.

    (6) create feature flag kWinUseBrowserSpellChecker.
          In order to enable runtime switch between two spellcheck services.
          We need to have a feature flag to indicate which spellcheck
          services to use. I created kWinUseBrowserSpellChecker. The flag
          only has effect on Windows.

    (7) Create spellcheck::UseBrowserSpellChecker()
          In order to enable runtime switch between platform specific
          spellcheck and hunspell spellcheck, we need a runtime check
          instead of build time check. I created a runtime check an put it
          in file spellcheck_features.cc. For Windows, the method will check
          for feature flag kWinUseBrowserSpellChecker to determine which
          spellcheck service to use. On all other platforms, it will return
          build time flag.

    After these steps, we enabled Windows Spellcheck Services integration
    and also achieved runtime switch between platform spellchecker and
    hunspell spellchecker for windows platform.

    Bug: 463364

chromium_src/chrome/browser/renderer_context_menu/render_view_context_menu.cc

@@ -7,26 +7,19 @@
 #include "brave/browser/profiles/profile_util.h"
 #include "brave/browser/tor/buildflags.h"
 #include "brave/browser/translate/buildflags/buildflags.h"
-#include "components/spellcheck/spellcheck_buildflags.h"
-#if !BUILDFLAG(USE_BROWSER_SPELLCHECKER)
 #include "brave/browser/renderer_context_menu/brave_spelling_options_submenu_observer.h"
-#endif
 
 // Our .h file creates a masquerade for RenderViewContextMenu.  Switch
 // back to the Chromium one for the Chromium implementation.
 #undef RenderViewContextMenu
 #define RenderViewContextMenu RenderViewContextMenu_Chromium
 
-#if !defined(OS_MACOSX)
 // Use our subclass to initialize SpellingOptionsSubMenuObserver.
 #define SpellingOptionsSubMenuObserver BraveSpellingOptionsSubMenuObserver
-#endif
 
 #include "../../../../chrome/browser/renderer_context_menu/render_view_context_menu.cc"  // NOLINT
 
-#if !defined(OS_MACOSX)
 #undef SpellingOptionsSubMenuObserver
-#endif
 
 // Make it clear which class we mean here.
 #undef RenderViewContextMenu