DevTools: rename debugger/ to devtools/, move DevTools files into content/renderer/devtools.

content/browser/debugger/manual_tests/resources/fib.js

-function fib(n) {
-  return n < 2 ? 1 : fib(n - 1) + fib(n - 2);
-}
-
-function eternal_fib() {
-  var started = Date.now();
-  while(true) {
-    fib(20);
-    // Make page responsive by making a break every 100 ms.
-    if (Date.now() - started >= 100) {
-      setTimeout(eternal_fib, 0);
-      return;
-    }
-  }
-}
-
-function run_fib() {
-  // Let the page do initial rendering, then go.
-  setTimeout(eternal_fib, 200);
-}