[WIP] WebFonts cache-aware timeout adaption

third_party/WebKit/Source/core/css/CSSFontFaceSrcValue.cpp

 /*
  * Copyright (C) 2007, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
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@@ skipping 70 matching lines @@
     return;
 
   request.setCrossOriginAccessControl(securityOrigin,
                                       CrossOriginAttributeAnonymous);
 }
 
 FontResource* CSSFontFaceSrcValue::fetch(Document* document) const {
   if (!m_fetched) {
     FetchRequest request(ResourceRequest(m_absoluteResource),
                          FetchInitiatorTypeNames::css);
+    request.mutableResourceRequest().setIsCacheAwareLoadingEnabled(true);

[Kunihiko Sakamoto, 2016/10/03 08:31:38]

I think we should do cache-aware loading only for @font-faces with font-display:
(swap | fallback | optional).
See the table in Toyoshima-san's doc:
https://docs.google.com/document/d/1SKRVFza_USrdVZgJmPnKWmqbzj-kVoxMB2ECH_xLh...

[Takashi Toyoshima, 2016/10/03 09:01:04]

Since it will introduce additional complexity, we would use cache-aware loading
always for WebFonts. This decision is based on data that requests rarely miss
the cache and disk check is reasonable fast compared to network access in the
case of cache miss.

But, probably we should make this feature behind a flag.

shao, can you add a new Runtime flag in
Source/platform/RuntimeEnabledFeatures.in, and set it only when the runtime flag
is set?
Probably, it should contain status=experimental so that it is enabled in tests
or users who enable chrome://flags/#enable-experimental-web-platform-features

[Shao-Chuan Lee, 2016/10/04 09:08:04]

Done.

     request.setContentSecurityCheck(m_shouldCheckContentSecurityPolicy);
     SecurityOrigin* securityOrigin = document->getSecurityOrigin();
     setCrossOriginAccessControl(request, securityOrigin);
     request.mutableResourceRequest().setHTTPReferrer(
         SecurityPolicy::generateReferrer(m_referrer.referrerPolicy,
                                          request.url(), m_referrer.referrer));
     FontResource* resource = FontResource::fetch(request, document->fetcher());
     if (!resource)
       return nullptr;
     m_fetched = FontResourceHelper::create(resource);
@@ skipping 28 matching lines @@
       ResourceFetcher::ResourceLoadingFromCache);
 }
 
 bool CSSFontFaceSrcValue::equals(const CSSFontFaceSrcValue& other) const {
   return m_isLocal == other.m_isLocal && m_format == other.m_format &&
          m_specifiedResource == other.m_specifiedResource &&
          m_absoluteResource == other.m_absoluteResource;
 }
 
 }  // namespace blink