headless: Require the user to pass in an initial URL

headless/app/headless_shell.cc

Index: headless/app/headless_shell.cc
diff --git a/headless/app/headless_shell.cc b/headless/app/headless_shell.cc
index e2d6348cf4285589d62c1a61f0ce7f2c113cf190..1031dbd5446b78a4fa95d7981971fc1a9faca677 100644
--- a/headless/app/headless_shell.cc
+++ b/headless/app/headless_shell.cc
@@ -37,8 +37,6 @@ class HeadlessShell : public HeadlessWebContents::Observer {
 
   void OnStart(HeadlessBrowser* browser) {
     browser_ = browser;
-    web_contents_ = browser->CreateWebContents(gfx::Size(800, 600));
-    web_contents_->AddObserver(this);
 
     base::CommandLine::StringVector args =
         base::CommandLine::ForCurrentProcess()->GetArgs();
@@ -50,11 +48,13 @@ class HeadlessShell : public HeadlessWebContents::Observer {
     } else {
       url = GURL(args[0]);
     }
-    if (!web_contents_->OpenURL(url)) {
+    web_contents_ = browser->CreateWebContents(url, gfx::Size(800, 600));
+    if (!web_contents_) {
       LOG(ERROR) << "Navigation failed";
-      web_contents_ = nullptr;
       browser_->Shutdown();
+      return;
     }
+    web_contents_->AddObserver(this);
   }
 
   void ShutdownIfNeeded() {
@@ -71,8 +71,6 @@ class HeadlessShell : public HeadlessWebContents::Observer {
     ShutdownIfNeeded();
   }
 
-  void DidFinishNavigation(bool success) override {}
-
  private:
   HeadlessBrowser* browser_;  // Not owned.
   std::unique_ptr<HeadlessWebContents> web_contents_;