Convert spellcheck to a buildflag header.

components/spellcheck/common/spellcheck_messages.h

Index: components/spellcheck/common/spellcheck_messages.h
diff --git a/components/spellcheck/common/spellcheck_messages.h b/components/spellcheck/common/spellcheck_messages.h
index 49ef8020c1fa0e4f648581751318938a3a9b71e4..60caa60e5ced2da8f67706aff7637955402d3d72 100644
--- a/components/spellcheck/common/spellcheck_messages.h
+++ b/components/spellcheck/common/spellcheck_messages.h
@@ -10,10 +10,11 @@
 #include "components/spellcheck/common/spellcheck_bdict_language.h"
 #include "components/spellcheck/common/spellcheck_marker.h"
 #include "components/spellcheck/common/spellcheck_result.h"
+#include "components/spellcheck/spellcheck_build_features.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_platform_file.h"
 
-#if !defined(ENABLE_SPELLCHECK)
+#if !BUILDFLAG(ENABLE_SPELLCHECK)
 #error "Spellcheck should be enabled"
 #endif
 
@@ -65,7 +66,7 @@ IPC_MESSAGE_CONTROL0(SpellCheckMsg_RequestDocumentMarkers)
 IPC_MESSAGE_CONTROL1(SpellCheckHostMsg_RespondDocumentMarkers,
                      std::vector<uint32_t> /* document marker identifiers */)
 
-#if !defined(USE_BROWSER_SPELLCHECKER)
+#if !BUILDFLAG(USE_BROWSER_SPELLCHECKER)
 // Sends text-check results from the Spelling service when the service finishes
 // checking text received by a SpellCheckHostMsg_CallSpellingService message.
 // If the service is not available, the 4th parameter should be false and the
@@ -77,7 +78,7 @@ IPC_MESSAGE_ROUTED4(SpellCheckMsg_RespondSpellingService,
                     std::vector<SpellCheckResult>)
 #endif
 
-#if defined(USE_BROWSER_SPELLCHECKER)
+#if BUILDFLAG(USE_BROWSER_SPELLCHECKER)
 // This message tells the renderer to advance to the next misspelling. It is
 // sent when the user clicks the "Find Next" button on the spelling panel.
 IPC_MESSAGE_ROUTED0(SpellCheckMsg_AdvanceToNextMisspelling)
@@ -104,7 +105,7 @@ IPC_MESSAGE_ROUTED2(SpellCheckHostMsg_NotifyChecked,
                     base::string16 /* word */,
                     bool /* true if checked word is misspelled */)
 
-#if !defined(USE_BROWSER_SPELLCHECKER)
+#if !BUILDFLAG(USE_BROWSER_SPELLCHECKER)
 // Asks the Spelling service to check text. When the service finishes checking
 // the input text, it sends a SpellingCheckMsg_RespondSpellingService with
 // text-check results.
@@ -115,7 +116,7 @@ IPC_MESSAGE_CONTROL4(SpellCheckHostMsg_CallSpellingService,
                      std::vector<SpellCheckMarker> /* markers */)
 #endif
 
-#if defined(USE_BROWSER_SPELLCHECKER)
+#if BUILDFLAG(USE_BROWSER_SPELLCHECKER)
 // Tells the browser to display or not display the SpellingPanel
 IPC_MESSAGE_ROUTED1(SpellCheckHostMsg_ShowSpellingPanel,
                     bool /* if true, then show it, otherwise hide it*/)