DevTools: fix co-existance of multiple DevTools extensions

LayoutTests/http/tests/inspector/resources/extension-main.js

 function trimURL(url)
 {
     if (!url)
         return;
     if (/^data:/.test(url))
         return url.replace(/,.*$/, "...");
     return url.replace(/.*\//, ".../");
 }
 
 function dumpObject(object, nondeterministicProps, prefix, firstLinePrefix)
@@ skipping 63 matching lines @@
 
 function runTests()
 {
     output("Running tests...");
     var tests = [];
     for (var symbol in this) {
         if (/^extension_test/.test(symbol) && typeof this[symbol] === "function")
             tests.push(symbol);
     }
     tests = tests.sort();
-    var testChain = onTestsDone;
+    var testChain = extension_onTestsDone;
     for (var test = tests.pop(); test; test = tests.pop())
         testChain = bind(runTest, this, bind(this[test], this, testChain), test);
     testChain();
 }
 
-function onTestsDone()
+function extension_onTestsDone()
 {
     output("All tests done.");
     evaluateOnFrontend("InspectorTest.completeTest();");
 }
 
 function runTest(test, name)
 {
     output("RUNNING TEST: " + name);
     try {
         test();
@@ skipping 10 matching lines @@
         nextTest.call(this);
     }
     return callbackWrapper;
 }
 
 function bind(func, thisObject)
 {
     var args = Array.prototype.slice.call(arguments, 2);
     return function() { return func.apply(thisObject, args.concat(Array.prototype.slice.call(arguments, 0))); };
 }