RenderTextMac: Fix crash when passed an invalid font.

ui/gfx/render_text_mac.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_RENDER_TEXT_MAC_H_
 #define UI_GFX_RENDER_TEXT_MAC_H_
 
 #include <ApplicationServices/ApplicationServices.h>
 #include <stddef.h>
 #include <stdint.h>
@@ skipping 13 matching lines @@
 //
 // Note: The current implementation only supports drawing and sizing the text,
 //       but not text selection or cursor movement.
 class GFX_EXPORT RenderTextMac : public RenderText {
  public:
   RenderTextMac();
   ~RenderTextMac() override;
 
   // RenderText:
   std::unique_ptr<RenderText> CreateInstanceOfSameType() const override;
+  void SetFontList(const FontList& font_list) override;
   bool MultilineSupported() const override;
   const base::string16& GetDisplayText() override;
   Size GetStringSize() override;
   SizeF GetStringSizeF() override;
   SelectionModel FindCursorPosition(const Point& point) override;
   bool IsSelectionSupported() const override;
   std::vector<FontSpan> GetFontSpansForTesting() override;
 
  protected:
   // RenderText:
@@ skipping 88 matching lines @@
 
   // Indicates that |runs_| are valid, set by |ComputeRuns()|.
   bool runs_valid_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderTextMac);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_MAC_H_