Convert spellcheck to a buildflag header.

chrome/renderer/DEPS

 include_rules = [
   "+chrome/grit",
   "+components/autofill/content/common",
   "+components/autofill/content/renderer",
   "+components/autofill/core/common",
   "+components/cdm/renderer",
   "+components/content_settings/core/common",
   "+components/contextual_search/renderer",
   "+components/crx_file",
   "+components/data_reduction_proxy/core/common",
   "+components/dom_distiller/content/common",
   "+components/dom_distiller/content/renderer",
   "+components/dom_distiller/core",
   "+components/grit",
   "+components/guest_view/renderer",
   "+components/metrics/leak_detector",
   "+components/metrics/proto",
   "+components/nacl/common",
   "+components/nacl/renderer",
   "+components/network_hints/renderer",
   "+components/password_manager/content/renderer",
   "+components/password_manager/core/common",
   "+components/pdf/renderer",
   "+components/plugins/renderer",
   "+components/printing/common",
   "+components/printing/renderer",
   "+components/rappor/public/interfaces",
   "+components/signin/core/common",
-  "+components/spellcheck/common",
-  "+components/spellcheck/renderer",
+  "+components/spellcheck",
+  "-components/spellcheck/browser",  # Allow all spellcheck but browser.
   "+components/startup_metric_utils/common",
   "+components/strings/grit",
   "+components/subresource_filter/content/renderer",
   "+components/translate/content/common",
   "+components/translate/content/renderer",
   "+components/translate/core/common",
   "+components/translate/core/language_detection",
   "+components/version_info",
   "+components/visitedlink/renderer",
   "+components/web_cache/renderer",
@@ skipping 12 matching lines @@
   "+skia",
   "+storage/common",
 ]
 
 specific_include_rules = {
   "chrome_content_renderer_client_browsertest\.cc" : [
     "+chrome/browser/ui",
     "+chrome/browser/ui/tabs",
   ],
 }