RenderTextHarfBuzz: Check CreateSkiaTypeface return value against NULL

ui/gfx/render_text.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_H_
 #define UI_GFX_RENDER_TEXT_H_
 
 #include <algorithm>
 #include <cstring>
 #include <string>
@@ skipping 157 matching lines @@
   Size size;
 
   // Sum of preceding lines' heights.
   int preceding_heights;
 
   // Maximum baseline of all segments on this line.
   int baseline;
 };
 
 // Creates an SkTypeface from a font |family| name and a |gfx::Font::FontStyle|.
+// May return NULL.
 skia::RefPtr<SkTypeface> CreateSkiaTypeface(const std::string& family,
                                             int style);
 
 }  // namespace internal
 
 // RenderText represents an abstract model of styled text and its corresponding
 // visual layout. Support is built in for a cursor, a selection, simple styling,
 // complex scripts, and bi-directional text. Implementations provide mechanisms
 // for rendering and translation between logical and visual data.
 class GFX_EXPORT RenderText {
@@ skipping 532 matching lines @@
   // Lines computed by EnsureLayout. These should be invalidated with
   // ResetLayout and on |display_rect_| changes.
   std::vector<internal::Line> lines_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderText);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_RENDER_TEXT_H_