fix(setInputFiles): make it work with CSP enabled (#3756)

We used to do fetch() to decode the file buffer. However, this is
blocked by strict CSP policy. Instead, we can use explicit
string -> bytes conversion, and trade performance for CSP compliance.

src/server/injected/injectedScript.ts

@@ -452,7 +452,7 @@ export class InjectedScript {
     throw new Error('Not a checkbox');
   }
 
-  async setInputFiles(node: Node, payloads: { name: string, mimeType: string, buffer: string }[]) {
+  setInputFiles(node: Node, payloads: { name: string, mimeType: string, buffer: string }[]) {
     if (node.nodeType !== Node.ELEMENT_NODE)
       return 'Node is not of type HTMLElement';
     const element: Element | undefined = node as Element;
@@ -463,10 +463,10 @@ export class InjectedScript {
     if (type !== 'file')
       return 'Not an input[type=file] element';
 
-    const files = await Promise.all(payloads.map(async file => {
-      const result = await fetch(`data:${file.mimeType};base64,${file.buffer}`);
-      return new File([await result.blob()], file.name, {type: file.mimeType});
-    }));
+    const files = payloads.map(file => {
+      const bytes = Uint8Array.from(atob(file.buffer), c => c.charCodeAt(0));
+      return new File([bytes], file.name, { type: file.mimeType });
+    });
     const dt = new DataTransfer();
     for (const file of files)
       dt.items.add(file);

test/page-set-input-files.spec.ts

@@ -115,6 +115,15 @@ it('should work when file input is not attached to DOM', async ({page, server})
   expect(chooser).toBeTruthy();
 });
 
+it('should work with CSP', async ({page, server}) => {
+  server.setCSP('/empty.html', 'default-src "none"');
+  await page.goto(server.EMPTY_PAGE);
+  await page.setContent(`<input type=file>`);
+  await page.setInputFiles('input', path.join(__dirname, '/assets/file-to-upload.txt'));
+  expect(await page.$eval('input', input => input.files.length)).toBe(1);
+  expect(await page.$eval('input', input => input.files[0].name)).toBe('file-to-upload.txt');
+});
+
 it('should respect timeout', async ({page, playwright}) => {
   let error = null;
   await page.waitForEvent('filechooser', {timeout: 1}).catch(e => error = e);