Adding a benchmark that measures the performance of using a single font for measuring text

PerformanceTests/Canvas/setFontAndMeasureTextSingleFont.html

Index: PerformanceTests/Canvas/setFontAndMeasureTextSingleFont.html
diff --git a/PerformanceTests/Canvas/setFontAndMeasureText.html b/PerformanceTests/Canvas/setFontAndMeasureTextSingleFont.html
similarity index 79%
copy from PerformanceTests/Canvas/setFontAndMeasureText.html
copy to PerformanceTests/Canvas/setFontAndMeasureTextSingleFont.html
index 9212cc0e22bc3276d18fff57867fe6334fb5520f..11f8bcc4fd8060317349099514fed235307911d4 100644
--- a/PerformanceTests/Canvas/setFontAndMeasureText.html
+++ b/PerformanceTests/Canvas/setFontAndMeasureTextSingleFont.html
@@ -7,20 +7,17 @@
 var canvas = document.createElement("canvas");
 var ctx = canvas.getContext("2d");
 var font1 = "bold 15px Arial";
-var font2 = "italic 20pt Calibri";
 
 function doTest() {
     ctx.font = font1;
     ctx.measureText("a");
-    ctx.font = font2;
-    ctx.measureText("b");
 }
 
 // Warm up the caches
 doTest();
 
 PerfTestRunner.measureRunsPerSecond({
-    description: "Measures performance of setting the current font and measuring text on a canvas.",
+    description: "Measures performance of setting the current font and measuring text using the same font over and over.",
     run: doTest
 });
 </script>