Reland r172943 "Make CSSFontFace::willUseFontData() load fonts with unicode-range"

Source/core/rendering/RenderText.cpp

Index: Source/core/rendering/RenderText.cpp
diff --git a/Source/core/rendering/RenderText.cpp b/Source/core/rendering/RenderText.cpp
index 242ca26d774679a5c6297652f00eab8ab28161a8..4243c39a93dcf01a9bbfd27b84c3308f02073834 100644
--- a/Source/core/rendering/RenderText.cpp
+++ b/Source/core/rendering/RenderText.cpp
@@ -205,8 +205,11 @@ void RenderText::styleDidChange(StyleDifference diff, const RenderStyle* oldStyl
     if (oldTransform != newStyle->textTransform() || oldSecurity != newStyle->textSecurity())
         transformText();
 
+    // This is an optimization that kicks off font load before layout.
+    // In order to make it fast, we only check if the first character of the
+    // text is included in the unicode ranges of the fonts.
     if (!text().containsOnlyWhitespace())
-        newStyle->font().willUseFontData();
+        newStyle->font().willUseFontData(text().characterStartingAt(0));
 }
 
 void RenderText::removeAndDestroyTextBoxes()