Move BrowserMessageFilter to public, and into content namespace.

chrome/browser/spellchecker/spellcheck_platform_mac.h

Index: chrome/browser/spellchecker/spellcheck_platform_mac.h
diff --git a/chrome/browser/spellchecker/spellcheck_platform_mac.h b/chrome/browser/spellchecker/spellcheck_platform_mac.h
index 89db07247f24234cc94f468ae41c4b1f5e382e71..3403af5ca6212304e63340cab31eec50ec5dad57 100644
--- a/chrome/browser/spellchecker/spellcheck_platform_mac.h
+++ b/chrome/browser/spellchecker/spellcheck_platform_mac.h
@@ -15,7 +15,9 @@
 #include "base/callback_forward.h"
 #include "base/string16.h"
 
+namespace content {
 class BrowserMessageFilter;
+}  // namespace content
 
 namespace spellcheck_mac {
 
@@ -87,7 +89,7 @@ void RequestTextCheck(int route_id,
                       int identifier,
                       int document_tag,
                       const string16& text,
-                      BrowserMessageFilter* destination);
+                      content::BrowserMessageFilter* destination);
 
 }  // namespace spellcheck_mac