WebFonts: show a console message when an intervention is triggered

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

Index: third_party/WebKit/Source/core/css/RemoteFontFaceSource.cpp
diff --git a/third_party/WebKit/Source/core/css/RemoteFontFaceSource.cpp b/third_party/WebKit/Source/core/css/RemoteFontFaceSource.cpp
index d40bb31c98cc1b6a13912e9240022a8f5676a677..4e4895c7e6a274c278130717dc5f49c432bfa9b6 100644
--- a/third_party/WebKit/Source/core/css/RemoteFontFaceSource.cpp
+++ b/third_party/WebKit/Source/core/css/RemoteFontFaceSource.cpp
@@ -34,6 +34,7 @@ RemoteFontFaceSource::RemoteFontFaceSource(FontResource* font, CSSFontSelector*
     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()));
     }
 }