Allow the default generic font family settings to find the first available font

ui/gfx/font.cc

Index: ui/gfx/font.cc
diff --git a/ui/gfx/font.cc b/ui/gfx/font.cc
index ac7b7491a6cdcb98caa8e889900db693f454d9f6..e19ac7dc7aeca181fd01a567f3421066f6f41592 100644
--- a/ui/gfx/font.cc
+++ b/ui/gfx/font.cc
@@ -4,8 +4,11 @@
 
 #include "ui/gfx/font.h"
 
+#include "base/strings/string_split.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
+#include "third_party/skia/include/core/SkTypeface.h"
+#include "third_party/skia/include/ports/SkFontMgr.h"
 #include "ui/gfx/platform_font.h"
 
 namespace gfx {
@@ -91,6 +94,34 @@ NativeFont Font::GetNativeFont() const {
 }
 #endif
 
+namespace {

[msw, 2016/10/28 07:05:06]

nit: put anon namespaces at the top of the file.

[kojii, 2016/10/28 07:57:30]

Done.

+
+bool IsFontFamilyAvailable(const std::string& family, SkFontMgr* fontManager) {
+#if defined(OS_LINUX)
+  sk_sp<SkTypeface> typeface(
+      fontManager->legacyCreateTypeface(family.c_str(), SkFontStyle()));
+  return typeface;
+#else
+  sk_sp<SkFontStyleSet> set(fontManager->matchFamily(family.c_str()));
+  return set && set->count();
+#endif
+}
+
+}  // namespace
+
+std::string Font::FirstAvailableOrFirst(const std::string& font_name_list) {
+  std::vector<std::string> families = base::SplitString(
+      font_name_list, ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
+  if (families.empty())
+    return std::string();
+  sk_sp<SkFontMgr> fm(SkFontMgr::RefDefault());
+  for (const auto& family : families) {
+    if (IsFontFamilyAvailable(family, fm.get()))

[msw, 2016/10/28 07:05:06]

Is it worth skipping this and early-returning families[0] when there's only one?

[kojii, 2016/10/28 07:57:30]

Done, unlikely for now but still good to have it.

+      return family;
+  }
+  return families[0];
+}
+
 #ifndef NDEBUG
 std::ostream& operator<<(std::ostream& stream, const Font::Weight weight) {
   return stream << static_cast<int>(weight);