Make FontListImpl RefCountedThreadSafe

ui/gfx/platform_font.h

Index: ui/gfx/platform_font.h
diff --git a/ui/gfx/platform_font.h b/ui/gfx/platform_font.h
index 48e14cf99608ad0fb52cae9b2ef6b2763cb99f2f..30a17f19b02e037672fee1a20d1321aaf03007bd 100644
--- a/ui/gfx/platform_font.h
+++ b/ui/gfx/platform_font.h
@@ -19,7 +19,8 @@ namespace gfx {
 class Font;
 struct FontRenderParams;
 
-class GFX_EXPORT PlatformFont : public base::RefCounted<PlatformFont> {
+class GFX_EXPORT PlatformFont
+    : public base::RefCountedThreadSafe<PlatformFont> {
  public:
   // Creates an appropriate PlatformFont implementation.
   static PlatformFont* CreateDefault();
@@ -85,7 +86,7 @@ class GFX_EXPORT PlatformFont : public base::RefCounted<PlatformFont> {
   virtual ~PlatformFont() {}
 
  private:
-  friend class base::RefCounted<PlatformFont>;
+  friend class base::RefCountedThreadSafe<PlatformFont>;
 };
 
 }  // namespace gfx