Improve the reliability and accuracy of SVG getTotalLength

LayoutTests/svg/custom/path-getTotalLength.svg

 <svg xmlns="http://www.w3.org/2000/svg">
     <g id='log' />
     <script>
     <![CDATA[
         if (window.testRunner)
             testRunner.dumpAsText();
         
         var svgNS = "http://www.w3.org/2000/svg";
         var pathElement = document.createElementNS(svgNS, 'path');
-        var errorTolerance = .1;
         
         var logOffset = 20;
         function result(didPass, string) {
           var newText = document.createElementNS(svgNS, "text");
           newText.setAttribute("x", 10);
           newText.setAttribute("y", logOffset);
           logOffset += 20;
           newText.textContent = string;
           var newTspan = document.createElementNS(svgNS, "tspan");
           if (didPass) {
             newTspan.textContent = "PASS: ";
             newTspan.style.fill = "green";
           } else {
             newTspan.textContent = "FAIL: ";
             newTspan.style.fill = "red";
           }
           newText.insertBefore(newTspan, newText.firstChild);
           document.getElementById('log').appendChild(newText);
         }
         
-        function expectLength(path, expectedLength) {
+        function expectLength(path, expectedLength, errorTolerance) {
             pathElement.setAttribute("d", path);
             
             var actualLength;
             try {
                 actualLength = pathElement.getTotalLength();
                 if (Math.abs(actualLength - expectedLength) < errorTolerance)
-                    result(true, path + "\" = " + actualLength);
+                    result(true, path + " = " + actualLength);
                 else
-                    result(false, path + "\" expected: " + expectedLength + " actual: " + actualLength);
+                    result(false, path + " expected: " + expectedLength + " actual: " + actualLength);
             } catch(e) {
-                result(false, path + "\" expected: " + expectedLength + " got exception: " + e);
+                result(false, path + " expected: " + expectedLength + " got exception: " + e);
             }
         }
         
         var errorCount = 0;
         
         // Tests go here:
-        expectLength('M 0 0 L 100 0 L 100 100 L 0 100 Z', 400);
-        expectLength('M 0 0 l 100 0 l 0 100 l -100 0 Z', 400);
-        expectLength('M 0 0 t 0 100', 100);
-        expectLength('M 0 0 Q 55 50 100 100', 141.4);  // I'm not sure if this is actually right
+        expectLength('M 0 0 L 100 0 L 100 100 L 0 100 Z', 400, 0.000001);
+        expectLength('M 0 0 l 100 0 l 0 100 l -100 0 Z', 400, 0.000001);
+        expectLength('M 0 0 t 0 100', 100, 0.1);
+        expectLength('M 0 0 Q 55 50 100 100', 141.4803314, 0.000001);
+        expectLength('M 778.4191616766467 375.19086364081954 C 781.239563 375.1908569 786.8525244750526 346.60170830052556 786.8802395209582 346.87991373394766', 29.86020, 0.0001);
+        expectLength('M 0 0 C 0.00001 0.00001 0.00002 0.00001 0.00003 0', 0.0000344338, 0.000000001);
     ]]>
     </script>
 </svg>