Improve usefulness of webglcontextcreationerror statusMessage

third_party/WebKit/LayoutTests/fast/canvas/webgl/webgl-error-response.html

 <!-- This is a test for crbug.com/412440, tests meaningful information in
 WebGL context creation error message. -->
 <script src="../../../resources/js-test.js"></script>
 <canvas id="webgl-canvas" width="200" height="200" class="nomargin"></canvas>
 <script>
 function main()
 {
   if (!window.testRunner) {
     testFailed("Requires window.testRunner");
   } else {
     initTest();
   }
 }
 
 function initTest() {
   var canvas = document.getElementById("webgl-canvas");
   testRunner.forceNextWebGLContextCreationToFail();
   canvas.addEventListener("webglcontextcreationerror", onContextCreationError, false);
   var gl = canvas.getContext("webgl");
   testRunner.dumpAsText();
 }
 
 function onContextCreationError(e) {
+  if (e.statusMessage.length == 0) {
+    testFailed("webglcontextcreationerror test failed");
+    return;
+  }
   var splitStatus = e.statusMessage.split(",");
-  var stringLocator = 1;
-  var status = true;
-  // Start iterating from 1 as , the initial message has no data.
+  var error =  "";
   for (var i = 1; i < splitStatus.length; i++) {
     var gpuInfoStr = splitStatus[i].split(" = ");
-    if (gpuInfoStr[stringLocator] == "")
-      status = false;
+    var key = gpuInfoStr[0].trim();
+    var value = gpuInfoStr[1];
+    if (key == "DEVICE" && (value == "0x0000" || value == ""))
+      error = error + "DeviceID is null.";
+    if (key == "VENDOR" && (value == "0x0000" || value == ""))
+      error = error + "VendorID is null.";
   }
-  if(status)
+  if (error.length)
+    testFailed("webglcontextcreationerror test failed " + error);
+  else
     testPassed("Status message displayed for webglcontextcreationerror");
-  else
-    testFailed("Context creation error test failed");
 }
 main();
 </script>