[DO NOT COMMIT] Trace events for layout-based First Meaningful Paint detection

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

Index: third_party/WebKit/Source/core/css/FontFaceSet.cpp
diff --git a/third_party/WebKit/Source/core/css/FontFaceSet.cpp b/third_party/WebKit/Source/core/css/FontFaceSet.cpp
index d065ba3195d52646edec61c49c46497d84feeb7c..ddaba8251bf2a4fb96921bdcf4120e3b2cf88aad 100644
--- a/third_party/WebKit/Source/core/css/FontFaceSet.cpp
+++ b/third_party/WebKit/Source/core/css/FontFaceSet.cpp
@@ -232,6 +232,15 @@ void FontFaceSet::loadError(FontFace* fontFace)
     removeFromLoadingFonts(fontFace);
 }
 
+bool FontFaceSet::hasBlankText() const
+{
+    for (auto& fontFace : m_loadingFonts) {
+        if (fontFace->isBlank())
+            return true;
+    }
+    return false;
+}
+
 void FontFaceSet::addToLoadingFonts(FontFace* fontFace)
 {
     if (!m_isLoading) {
@@ -508,6 +517,13 @@ void FontFaceSet::didLayout(Document& document)
         fonts->didLayout();
 }
 
+bool FontFaceSet::hasBlankText(Document& document)
+{
+    if (FontFaceSet* fonts = static_cast<FontFaceSet*>(Supplement<Document>::from(document, supplementName())))
+        return fonts->hasBlankText();
+    return false;
+}
+
 FontFaceSetIterable::IterationSource* FontFaceSet::startIteration(ScriptState*, ExceptionState&)
 {
     // Setlike should iterate each item in insertion order, and items should