SuperSize: Viewer: Infer JS or Wasm backend from extension

Bug: 1011921
Change-Id: I88e87dc609307e68fffc9deb911b09ba6616e6f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1914545
Commit-Queue: Jasper Chapman-Black <jaspercb@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#715074}

tools/binary_size/libsupersize/start_server.py

@@ -22,7 +22,7 @@ class SupersizeHTTPRequestHandler(SimpleHTTPServer.SimpleHTTPRequestHandler,
   def translate_path(self, path):
     f = super(SupersizeHTTPRequestHandler, self).translate_path(path)
     relative_path = os.path.relpath(f, os.getcwd())
-    if relative_path == 'data.ndjson':
+    if relative_path in ['data.ndjson', 'data.size']:
       return SupersizeHTTPRequestHandler.data_file_path
     if relative_path == 'before.size':
       return SupersizeHTTPRequestHandler.before_file_path
@@ -59,8 +59,10 @@ def Run(args, _parser):
   httpd = BaseHTTPServer.HTTPServer(server_addr, SupersizeHTTPRequestHandler)
 
   sa = httpd.socket.getsockname()
-  before_suffix = '&before_url=before.size&wasm=1' if args.before_file else ''
+  is_ndjson = args.report_file.endswith('ndjson')
+  data_file = 'data.ndjson' if is_ndjson else 'data.size'
+  maybe_before_file = '&before_url=before.size' if args.before_file else ''
   logging.warning(
-      'Server ready at http://%s:%d/viewer.html?load_url=data.ndjson' +
-      before_suffix, sa[0], sa[1])
+      'Server ready at http://%s:%d/viewer.html?load_url=' + data_file +
+      maybe_before_file, sa[0], sa[1])
   httpd.serve_forever()

tools/binary_size/libsupersize/static/start-worker.js

@@ -7,8 +7,8 @@
 
 let _innerWorker = null;
 const urlParams = new URLSearchParams(window.location.search);
-if (urlParams.get('wasm')) {
-  console.log("wasm=1; Using WebAssembly web worker");
+if (urlParams.get('load_url').endsWith('.size')) {
+  console.log('Using WebAssembly web worker');
   _innerWorker = new Worker('tree-worker-wasm.js');
 } else {
   _innerWorker = new Worker('tree-worker.js');