Enable unused param checking for public includes.

src/ports/SkFontHost_linux.cpp

Index: src/ports/SkFontHost_linux.cpp
diff --git a/src/ports/SkFontHost_linux.cpp b/src/ports/SkFontHost_linux.cpp
index 0b99e6517ab6e51b943ecc1d4fc602ecd1fd0ec2..6003c095c164ee23125a34ca5ed0eedc00005d65 100644
--- a/src/ports/SkFontHost_linux.cpp
+++ b/src/ports/SkFontHost_linux.cpp
@@ -248,6 +248,13 @@ protected:
         return sset->matchStyle(fontStyle);
     }
 
+    virtual SkTypeface* onMatchFamilyStyleCharacter(const char familyName[], const SkFontStyle&,
+                                                    const char* bcp47[], int bcp47Count,
+                                                    SkUnichar character) const SK_OVERRIDE
+    {
+        return NULL;
+    }
+
     virtual SkTypeface* onMatchFaceStyle(const SkTypeface* familyMember,
                                          const SkFontStyle& fontStyle) const SK_OVERRIDE
     {