Webfont CORS-enabled fetching with fallback

Source/core/css/RemoteFontFaceSource.cpp

Index: Source/core/css/RemoteFontFaceSource.cpp
diff --git a/Source/core/css/RemoteFontFaceSource.cpp b/Source/core/css/RemoteFontFaceSource.cpp
index 9b15954c7a9aa06f6e7b13d21cf7c3732c9a05b7..565d1158e3eb8fd5299b5d44dbeddd7ccc68ad87 100644
--- a/Source/core/css/RemoteFontFaceSource.cpp
+++ b/Source/core/css/RemoteFontFaceSource.cpp
@@ -5,8 +5,11 @@
 #include "config.h"
 #include "core/css/RemoteFontFaceSource.h"
 
+#include "FetchInitiatorTypeNames.h"
 #include "core/css/CSSCustomFontData.h"
 #include "core/css/CSSFontFace.h"
+#include "core/css/CSSFontSelector.h"
+#include "core/fetch/ResourceFetcher.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/fonts/FontDescription.h"
 #include "platform/fonts/SimpleFontData.h"
@@ -82,6 +85,24 @@ void RemoteFontFaceSource::fontLoadWaitLimitExceeded(FontResource*)
     m_histograms.recordFallbackTime(m_font.get());
 }
 
+void RemoteFontFaceSource::corsFailed(FontResource*)
+{
+    pruneTable();
+
+    if (m_face) {
+        Document* document = m_face->fontSelector() ? m_face->fontSelector()->document() : 0;
+        if (document) {
+            FetchRequest request(ResourceRequest(m_font->url()), FetchInitiatorTypeNames::css);
+            m_font->removeClient(this);

[Kunihiko Sakamoto, 2014/04/09 10:24:18]

CSSFontFaceSrcValue have a reference to this FontResource too, and we're not
updating it. I'm not sure if this may cause any problem or not.

[bashi, 2014/04/10 03:40:56]

Thank you for pointing this out. But it's difficult to update the reference
because RemoteFontFaceSource, which is the client of FontResource, can't reach
CSSFontFaceSrcValue when CORS failure occurs. Updating it will require
non-trivial change in css module and I'm not sure it is worth to do it for this
tentative logic.

I added an 'invalidator' which clears the reference in CSSFontFaceSrcValue so
that calling CSSFontFaceSrcValue::fetch() won't return invalid FontResource at
least. Does this make sense?

+            m_font = document->fetcher()->fetchFont(request);
+            m_font->addClient(this);
+            m_face->fontSelector()->beginLoadingFontSoon(m_font.get());
+        } else {
+            m_face->fontLoaded(this);
+        }
+    }
+}
+
 PassRefPtr<SimpleFontData> RemoteFontFaceSource::createFontData(const FontDescription& fontDescription)
 {
     if (!isLoaded())
@@ -156,6 +177,12 @@ void RemoteFontFaceSource::FontLoadHistograms::recordRemoteFont(const FontResour
             : font->response().wasCached() ? Hit
             : Miss;
         blink::Platform::current()->histogramEnumeration("WebFont.CacheHit", histogramValue, CacheHitEnumMax);
+
+        if (!font->errorOccurred()) {
+            enum { CORSSuccess, CORSFail, CORSEnumMax };
+            int corsValue = font->options().corsEnabled == IsCORSEnabled ? CORSSuccess : CORSFail;
+            blink::Platform::current()->histogramEnumeration("WebFont.CORSSuccess", corsValue, CORSEnumMax);
+        }
     }
 }