Improve WebUI documentation.

- Format code to fit within 80 columns.
- Explain why HelloWorldDialog is created with the "new" operator.

Change-Id: Ic09f36552b52bec61b8e7e556361def7f4a7445b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3283535
Reviewed-by: dpapad <dpapad@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#942191}

docs/webui_in_chrome.md

@@ -248,7 +248,10 @@ HelloWorldUI::HelloWorldUI(content::WebUI* web_ui)
   html_source->UseStringsJs();
 
   // Add required resources.
-  webui::SetupWebUIDataSource(html_source, base::make_span(kHelloWorldResources, kHelloWorldResourcesSize), IDR_HELLO_WORLD_HELLO_WORLD_CONTAINER_HTML);
+  webui::SetupWebUIDataSource(
+      html_source,
+      base::make_span(kHelloWorldResources, kHelloWorldResourcesSize),
+      IDR_HELLO_WORLD_HELLO_WORLD_CONTAINER_HTML);
 
   content::BrowserContext* browser_context =
       web_ui->GetWebContents()->GetBrowserContext();
@@ -345,6 +348,7 @@ do that, some small changes are needed to your code.  First, we need to add a ne
 HelloWorldDialog::HelloWorldDialog() = default;
 
 void HelloWorldDialog::Show() {
+  // HelloWorldDialog is self-deleting via OnDialogClosed().
   chrome::ShowWebDialog(nullptr, ProfileManager::GetActiveUserProfile(),
                         new HelloWorldDialog());
 }