[headless] Add command line flag for default background color.

headless/app/headless_shell_switches.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 "headless/app/headless_shell_switches.h"
 
 namespace headless {
 namespace switches {
 
+// The background color to be used if the page doesn't specify one. Provided as
+// RGBA integer value in hex, e.g. 'ff0000ff' for red or '00000000' for
+// transparent.
+const char kDefaultBackgroundColor[] = "default-background-color";
+
 // The directory breakpad should store minidumps in.
 const char kCrashDumpsDir[] = "crash-dumps-dir";
 
 // Instructs headless_shell to cause network fetches to complete in order of
 // creation. This removes a significant source of network related
 // non-determinism at the cost of slower page loads.
 const char kDeterministicFetch[] = "deterministic-fetch";
 
 // Instructs headless_shell to print document.body.innerHTML to stdout.
 const char kDumpDom[] = "dump-dom";
@@ skipping 22 matching lines @@
 const char kScreenshot[] = "screenshot";
 
 // Issues a stop after the specified number of milliseconds.  This cancels all
 // navigation and causes the DOMContentLoaded event to fire.
 const char kTimeout[] = "timeout";
 
 // Sets the GL implementation to use. Use a blank string to disable GL
 // rendering.
 const char kUseGL[] = "use-gl";
 
+// A string used to override the default user agent with a custom one.
+const char kUserAgent[] = "user-agent";
+
 // Directory where the browser stores the user profile.
 const char kUserDataDir[] = "user-data-dir";
 
 // If set the system waits the specified number of virtual milliseconds before
 // deeming the page to be ready.  For determinism virtual time does not advance
 // while there are pending network fetches (i.e no timers will fire). Once all
 // network fetches have completed, timers fire and if the system runs out of
 // virtual time is fastforwarded so the next timer fires immediatley, until the
 // specified virtual time budget is exhausted.
 const char kVirtualTimeBudget[] = "virtual-time-budget";
 
 // Sets the initial window size. Provided as string in the format "800,600".
 const char kWindowSize[] = "window-size";
 
-// A string used to override the default user agent with a custom one.
-const char kUserAgent[] = "user-agent";
-
 }  // namespace switches
 }  // namespace headless