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

third_party/WebKit/Source/platform/fonts/FontCache.cpp

Index: third_party/WebKit/Source/platform/fonts/FontCache.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/FontCache.cpp b/third_party/WebKit/Source/platform/fonts/FontCache.cpp
index 2844a92e37aa811a9dd023d1d65441be65a5e5da..2f7a5f2e375108d54da7d67b10848c55d75f9b4a 100644
--- a/third_party/WebKit/Source/platform/fonts/FontCache.cpp
+++ b/third_party/WebKit/Source/platform/fonts/FontCache.cpp
@@ -48,6 +48,7 @@
 #include "platform/tracing/web_memory_allocator_dump.h"
 #include "platform/tracing/web_process_memory_dump.h"
 #include "public/platform/Platform.h"
+#include "ui/gfx/font.h"
 #include "wtf/HashMap.h"
 #include "wtf/ListHashSet.h"
 #include "wtf/PtrUtil.h"
@@ -303,6 +304,11 @@ bool FontCache::isPlatformFontAvailable(const FontDescription& fontDescription,
       checkingAlternateName);
 }
 
+String FontCache::firstAvailableOrFirst(const String& families) {
+  return String::fromUTF8(

[eae, 2016/10/26 16:59:36]

I don't suppose we could change gfx::Font::FirstAvailableOrFirst to take a
utf-16 string? If not this is fine but please add a comment explaining the
conversions.

[kojii, 2016/10/28 05:07:14]

I think it's possible, but after looking into it, I think it doesn't help much.
The only input string as of now are all ASCII, and gfx::Font needs to convert
the inputs to UTF-8 when it calls Skia. So from the perf perspective, the ideal
thing is gfx::Font::FirstAvailableOrFirst to have Latin1 string to avoid string
copies and convert between ASCII/UTF-8, but it looks like too specific.

GenericFontFamilySettings caches the result, so this is called at most 1 or 2
times per renderer/setting change/script, and probably only for a few scripts. I
think we're ok for now, and if the usage increases, I'm happy to look into
further to avoid the conversions and copies.

Added comment.

+      gfx::Font::FirstAvailableOrFirst(families.utf8().data()).c_str());
+}
+
 SimpleFontData* FontCache::getNonRetainedLastResortFallbackFont(
     const FontDescription& fontDescription) {
   return getLastResortFallbackFont(fontDescription, DoNotRetain).leakRef();