VR: Fix crash when fallback font is missing

chrome/browser/android/vr_shell/textures/ui_texture.cc

 // Copyright 2017 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.
 
 #include "chrome/browser/android/vr_shell/textures/ui_texture.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 37 matching lines @@
   // (which is not implemented for android yet) in order to avoid
   // querying per character.
 
   sk_sp<SkFontMgr> font_mgr(SkFontMgr::RefDefault());
   std::set<std::string> names;
   // TODO(acondor): Query BrowserProcess to obtain the application locale.
   for (base::i18n::UTF16CharIterator it(&text); !it.end(); it.Advance()) {
     sk_sp<SkTypeface> tf(font_mgr->matchFamilyStyleCharacter(
         default_font.GetFontName().c_str(), SkFontStyle(), nullptr, 0,
         it.get()));
+    if (!tf)
+      continue;

[cjgrant, 2017/04/25 16:40:06]

If we hit this, does it mean that some characters must render with the default
font?

[mthiesse, 2017/04/25 16:47:59]

Yes, I'll add a TODO to address this when we move to gfx::GetFallbackFonts, as
we can't address it here.

     SkString sk_name;
     tf->getFamilyName(&sk_name);
     std::string name(sk_name.c_str());
     if (name != kDefaultFontFamily)
       names.insert(name);
   }
   for (const auto& name : names)
     fonts.push_back(gfx::Font(name, size));
   return gfx::FontList(fonts);
 }
 
 }  // namespace vr_shell