VR: Fix crash when fallback font is missing

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

Index: chrome/browser/android/vr_shell/textures/ui_texture.cc
diff --git a/chrome/browser/android/vr_shell/textures/ui_texture.cc b/chrome/browser/android/vr_shell/textures/ui_texture.cc
index 36cab83305e983ae31bb12f71fad40df5287a19d..d07b2b60f44483433956716c8c03bc753551bad7 100644
--- a/chrome/browser/android/vr_shell/textures/ui_texture.cc
+++ b/chrome/browser/android/vr_shell/textures/ui_texture.cc
@@ -55,6 +55,8 @@ gfx::FontList UiTexture::GetFontList(int size, base::string16 text) {
     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());