Set WebFont priority to very low if the network is detected to be slow

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

 // Copyright 2014 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 "core/css/RemoteFontFaceSource.h"
 
 #include "core/css/CSSCustomFontData.h"
 #include "core/css/CSSFontFace.h"
 #include "core/css/CSSFontSelector.h"
 #include "core/dom/Document.h"
 #include "core/fetch/ResourceFetcher.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "core/loader/FrameLoaderClient.h"
 #include "core/page/NetworkStateNotifier.h"
 #include "platform/Histogram.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/fonts/FontDescription.h"
 #include "platform/fonts/SimpleFontData.h"
+#include "platform/network/ResourceLoadPriority.h"
 #include "public/platform/WebEffectiveConnectionType.h"
 #include "wtf/CurrentTime.h"
 
 namespace blink {
 
 namespace {
 
 bool isEffectiveConnectionTypeSlowFor(Document* document) {
   WebEffectiveConnectionType type =
       document->frame()->loader().client()->getEffectiveConnectionType();
@@ skipping 36 matching lines @@
   ThreadState::current()->registerPreFinalizer(this);
   m_font->addClient(this);
 
   if (shouldTriggerWebFontsIntervention()) {
     m_isInterventionTriggered = true;
     m_period = SwapPeriod;
     m_fontSelector->document()->addConsoleMessage(ConsoleMessage::create(
         OtherMessageSource, InfoMessageLevel,
         "Slow network is detected. Fallback font will be used while loading: " +
             m_font->url().elidedString()));
+    if (!font->url().protocolIsData() && !font->isLoaded() &&

[Takashi Toyoshima, 2016/11/14 03:53:56]

|font| is shared by multiple RemoteFontFaceSource instances.
So we may need to lower the priority only when all clients agreed.

[tbansal1, 2016/11/14 20:12:08]

Done.

+        m_display == FontDisplayAuto) {
+      m_font->didChangePriority(ResourceLoadPriorityVeryLow, 0);
+    }
   }
 }
 
 RemoteFontFaceSource::~RemoteFontFaceSource() {}
 
 void RemoteFontFaceSource::dispose() {
   m_font->removeClient(this);
   m_font = nullptr;
   pruneTable();
 }
@@ skipping 142 matching lines @@
   if (!temporaryFont) {
     ASSERT_NOT_REACHED();
     return nullptr;
   }
   RefPtr<CSSCustomFontData> cssFontData = CSSCustomFontData::create(
       this, m_period == BlockPeriod ? CSSCustomFontData::InvisibleFallback
                                     : CSSCustomFontData::VisibleFallback);
   return SimpleFontData::create(temporaryFont->platformData(), cssFontData);
 }
 
 void RemoteFontFaceSource::beginLoadIfNeeded() {

[Takashi Toyoshima, 2016/11/14 03:53:56]

This is called for each RemoteFontFaceSource instance, and if shared |m_font|
didn't start actual font loading, this instance kicks it.

This may be a possible place to change loading priority though still other
clients may need higher priorities later.

[tbansal1, 2016/11/14 20:12:08]

Done.

   if (m_fontSelector->document() && m_font->stillNeedsLoad()) {
     m_fontSelector->document()->fetcher()->startLoad(m_font);
     if (!m_font->isLoaded())
       m_font->startLoadLimitTimers();
     m_histograms.loadStarted();
   }
 
   if (m_face)
     m_face->didBeginLoad();
 }
@@ skipping 203 matching lines @@
       return Miss;
     case FromUnknown:
     // Fall through.
     default:
       NOTREACHED();
   }
   return Miss;
 }
 
 }  // namespace blink