WebFonts: show a console message when an intervention is triggered

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"
@@ skipping 16 matching lines @@
     , m_isInterventionTriggered(false)
 {
     ThreadState::current()->registerPreFinalizer(this);
     m_font->addClient(this);
 
     // TODO(crbug.com/578029): Connect NQE signal for V2 mode.
     bool triggered = RuntimeEnabledFeatures::webFontsInterventionV2Enabled() ? false : networkStateNotifier().connectionType() == WebConnectionTypeCellular2G;
     if (RuntimeEnabledFeatures::webFontsInterventionTriggerEnabled() || (triggered && display == FontDisplayAuto)) {
         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()));
     }
 }
 
 RemoteFontFaceSource::~RemoteFontFaceSource()
 {
 }
 
 void RemoteFontFaceSource::dispose()
 {
     m_font->removeClient(this);
@@ skipping 236 matching lines @@
         interventionResult |= 1 << 0;
     if (triggered)
         interventionResult |= 1 << 1;
     const int boundary = 1 << 2;
 
     DEFINE_STATIC_LOCAL(EnumerationHistogram, interventionHistogram, ("WebFont.InterventionResult", boundary));
     interventionHistogram.count(interventionResult);
 }
 
 } // namespace blink