Add UMA to measure font-display value

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

Index: third_party/WebKit/Source/core/css/FontFace.cpp
diff --git a/third_party/WebKit/Source/core/css/FontFace.cpp b/third_party/WebKit/Source/core/css/FontFace.cpp
index 6f908043004e40ca67323933b181fe063ba08cd5..2f4661d9dc67192a1e0ebcf29cf0d26a4db07a13 100644
--- a/third_party/WebKit/Source/core/css/FontFace.cpp
+++ b/third_party/WebKit/Source/core/css/FontFace.cpp
@@ -59,6 +59,7 @@
 #include "core/frame/UseCounter.h"
 #include "platform/FontFamilyNames.h"
 #include "platform/SharedBuffer.h"
+#include "public/platform/Platform.h"
 
 namespace blink {
 
@@ -600,6 +601,9 @@ void FontFace::initCSSFontFace(Document* document, PassRefPtrWillBeRawPtr<CSSVal
         if (source)
             m_cssFontFace->addSource(source.release());
     }
+
+    if (m_display)
+        Platform::current()->histogramEnumeration("WebFont.FontDisplayValue", CSSValueToFontDisplay(m_display.get()), FontDisplayEnumMax);
 }
 
 void FontFace::initCSSFontFace(const unsigned char* data, size_t size)