RenderTextMac: Fix crash when passed an invalid font.

ui/gfx/render_text_mac.mm

 // 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.
 
 #include "ui/gfx/render_text_mac.h"
 
 #import <AppKit/AppKit.h>
 #include <ApplicationServices/ApplicationServices.h>
 #include <CoreText/CoreText.h>
 
@@ skipping 43 matching lines @@
 
   base::ScopedCFTypeRef<CFStringRef> family_name(CTFontCopyFamilyName(font));
   CFDictionarySetValue(attributes, kCTFontNameAttribute, family_name.release());
 
   base::ScopedCFTypeRef<CTFontDescriptorRef> desc(
       CTFontDescriptorCreateWithAttributes(attributes));
   return base::ScopedCFTypeRef<CTFontRef>(
       CTFontCreateWithFontDescriptor(desc, 0.0, nullptr));
 }
 
+// Returns whether |font_list| has a valid primary native font.
+bool HasValidPrimaryNativeFont(const gfx::FontList& font_list) {
+  return font_list.GetPrimaryFont().GetNativeFont();
+}
+
+// Checks whether |font_list| is valid. If it isn't, returns the default font
+// list (or a font list derived from it). The returned font list will have a
+// valid primary native font.
+gfx::FontList GetValidFontList(const gfx::FontList& font_list) {
+  if (HasValidPrimaryNativeFont(font_list))
+    return font_list;
+
+  const gfx::FontList default_font_list;
+  const int size_delta =
+      font_list.GetFontSize() - default_font_list.GetFontSize();
+  const gfx::FontList derived_font_list = default_font_list.Derive(
+      size_delta, font_list.GetFontStyle(), font_list.GetFontWeight());
+  if (HasValidPrimaryNativeFont(derived_font_list))
+    return derived_font_list;
+
+  DCHECK(HasValidPrimaryNativeFont(default_font_list));
+  return default_font_list;
+}
+
 }  // namespace
 
 namespace gfx {
 
 namespace internal {
 
 // Note: this is only used by RenderTextHarfbuzz.
 sk_sp<SkTypeface> CreateSkiaTypeface(const Font& font,
                                      bool italic,
                                      Font::Weight weight) {
   const Font::FontStyle style = italic ? Font::ITALIC : Font::NORMAL;
   Font font_with_style = font.Derive(0, style, weight);
   if (!font_with_style.GetNativeFont())
     return nullptr;
 
   return sk_sp<SkTypeface>(SkCreateTypefaceFromCTFont(
       base::mac::NSToCFCast(font_with_style.GetNativeFont())));
 }
 
 }  // namespace internal
 
 RenderTextMac::RenderTextMac() : common_baseline_(0), runs_valid_(false) {}
 
 RenderTextMac::~RenderTextMac() {}
 
 std::unique_ptr<RenderText> RenderTextMac::CreateInstanceOfSameType() const {
   return base::WrapUnique(new RenderTextMac);
 }
 
+void RenderTextMac::SetFontList(const FontList& font_list) {
+  // Ensure the font list used has a valid native font.
+  RenderText::SetFontList(GetValidFontList(font_list));
+}
+
 bool RenderTextMac::MultilineSupported() const {
   return false;
 }
 
 const base::string16& RenderTextMac::GetDisplayText() {
   return text_elided() ? display_text() : layout_text();
 }
 
 Size RenderTextMac::GetStringSize() {
   SizeF size_f = GetStringSizeF();
@@ skipping 173 matching lines @@
   *baseline = ascent;
   return SizeF(width, std::max(ascent + descent + leading,
                                static_cast<CGFloat>(min_line_height())));
 }
 
 base::ScopedCFTypeRef<CTLineRef> RenderTextMac::EnsureLayoutInternal(
     const base::string16& text,
     base::ScopedCFTypeRef<CFMutableArrayRef>* attributes_owner) {
   CTFontRef ct_font =
       base::mac::NSToCFCast(font_list().GetPrimaryFont().GetNativeFont());
+  DCHECK(ct_font);
 
   const void* keys[] = {kCTFontAttributeName};
   const void* values[] = {ct_font};
   base::ScopedCFTypeRef<CFDictionaryRef> attributes(
       CFDictionaryCreate(NULL, keys, values, arraysize(keys), NULL,
                          &kCFTypeDictionaryValueCallBacks));
 
   base::ScopedCFTypeRef<CFStringRef> cf_text(base::SysUTF16ToCFStringRef(text));
   base::ScopedCFTypeRef<CFAttributedStringRef> attr_text(
       CFAttributedStringCreate(NULL, cf_text, attributes));
@@ skipping 162 matching lines @@
   // TODO(karandeepb): This is not invoked on any codepath currently. Style the
   // returned text if need be.
   if (obscured())
     return false;
 
   decorated_text->text = GetTextFromRange(range);
   return true;
 }
 
 }  // namespace gfx