Headless: expose WebPreferences to embedder, add --hide-scrollbars.

headless/app/headless_shell.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <iostream>
 #include <memory>
 #include <string>
 
 #include "base/base64.h"
 #include "base/bind.h"
@@ skipping 57 matching lines @@
       : browser_(nullptr),
         devtools_client_(HeadlessDevToolsClient::Create()),
         web_contents_(nullptr),
         processed_page_ready_(false),
         browser_context_(nullptr) {}
   ~HeadlessShell() override {}
 
   void OnStart(HeadlessBrowser* browser) {
     browser_ = browser;
 
+    HeadlessBrowserContext::Builder context_builder =
+        browser_->CreateBrowserContextBuilder();
     if (base::CommandLine::ForCurrentProcess()->HasSwitch(
             headless::switches::kDeterministicFetch)) {
       deterministic_dispatcher_.reset(
           new headless::DeterministicDispatcher(browser_->BrowserIOThread()));
 
       headless::ProtocolHandlerMap protocol_handlers;
       protocol_handlers[url::kHttpScheme] =
           base::MakeUnique<headless::DeterministicHttpProtocolHandler>(
               deterministic_dispatcher_.get(), browser->BrowserIOThread());
       protocol_handlers[url::kHttpsScheme] =
           base::MakeUnique<headless::DeterministicHttpProtocolHandler>(
               deterministic_dispatcher_.get(), browser->BrowserIOThread());
 
-      browser_context_ = browser_->CreateBrowserContextBuilder()
-                             .SetProtocolHandlers(std::move(protocol_handlers))
-                             .Build();
-    } else {
-      browser_context_ = browser_->CreateBrowserContextBuilder().Build();
+      context_builder.SetProtocolHandlers(std::move(protocol_handlers));
     }
+    if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+            headless::switches::kHideScrollbars)) {
+      context_builder.SetOverrideWebPreferencesCallback(
+          base::Bind([](headless::WebPreferences* preferences) {
+            preferences->hide_scrollbars = true;
+          }));
+    }
+    browser_context_ = context_builder.Build();
 
     HeadlessWebContents::Builder builder(
         browser_context_->CreateWebContentsBuilder());
     base::CommandLine::StringVector args =
         base::CommandLine::ForCurrentProcess()->GetArgs();
 
     // TODO(alexclarke): Should we navigate to about:blank first if using
     // virtual time?
     if (!args.empty() && !args[0].empty())
       builder.SetInitialURL(GURL(args[0]));
@@ skipping 322 matching lines @@
       LOG(ERROR) << "Malformed window size";
       return EXIT_FAILURE;
     }
     builder.SetWindowSize(parsed_window_size);
   }
 
   return HeadlessBrowserMain(
       builder.Build(),
       base::Bind(&HeadlessShell::OnStart, base::Unretained(&shell)));
 }