[headless] Call StopLocalDevToolsHttpHandler only when needed.

headless/lib/browser/headless_browser_main_parts.cc

 // Copyright 2015 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/lib/browser/headless_browser_main_parts.h"
 
 #include "headless/lib/browser/headless_browser_context_impl.h"
 #include "headless/lib/browser/headless_browser_impl.h"
 #include "headless/lib/browser/headless_devtools.h"
 #include "headless/lib/browser/headless_screen.h"
 #include "ui/aura/env.h"
 #include "ui/display/screen.h"
 
 namespace headless {
 
 namespace {
 
 void PlatformInitialize(const gfx::Size& screen_size) {
   HeadlessScreen* screen = HeadlessScreen::Create(screen_size);
   display::Screen::SetScreenInstance(screen);
 }
 
 void PlatformExit() {
 }
 
 }  // namespace
 
 HeadlessBrowserMainParts::HeadlessBrowserMainParts(HeadlessBrowserImpl* browser)
-    : browser_(browser) {}
+    : browser_(browser)
+    , devtools_http_handler_started_(false) {}
 
 HeadlessBrowserMainParts::~HeadlessBrowserMainParts() {}
 
 void HeadlessBrowserMainParts::PreMainMessageLoopRun() {
-  if (browser_->options()->devtools_endpoint.address().IsValid())
+  if (browser_->options()->devtools_endpoint.address().IsValid()) {
     StartLocalDevToolsHttpHandler(browser_->options());
+    devtools_http_handler_started_ = true;
+  }
   PlatformInitialize(browser_->options()->window_size);
 }
 
 void HeadlessBrowserMainParts::PostMainMessageLoopRun() {
-  StopLocalDevToolsHttpHandler();
+  if (devtools_http_handler_started_) {
+    StopLocalDevToolsHttpHandler();
+    devtools_http_handler_started_ = false;
+  }
   PlatformExit();
 }
 
 }  // namespace headless