[headless] Expose DevToolsTarget via HeadlessBrowser + add tracing test.

headless/lib/browser/headless_browser_impl.cc

Index: headless/lib/browser/headless_browser_impl.cc
diff --git a/headless/lib/browser/headless_browser_impl.cc b/headless/lib/browser/headless_browser_impl.cc
index 747639ca3f68c116562f531cef63a57c8e19a0b6..c21bb2cafc747159bf0f2b299da43d9754b0cff1 100644
--- a/headless/lib/browser/headless_browser_impl.cc
+++ b/headless/lib/browser/headless_browser_impl.cc
@@ -13,11 +13,13 @@
 #include "base/threading/thread_task_runner_handle.h"
 #include "content/public/app/content_main.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/devtools_agent_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/common/content_switches.h"
 #include "headless/app/headless_shell_switches.h"
 #include "headless/lib/browser/headless_browser_context_impl.h"
 #include "headless/lib/browser/headless_browser_main_parts.h"
+#include "headless/lib/browser/headless_devtools_client_impl.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
 #include "headless/lib/headless_content_main_delegate.h"
 #include "net/http/http_util.h"
@@ -32,6 +34,10 @@
 #include "sandbox/win/src/sandbox_types.h"
 #endif
 
+namespace content {
+class DevToolsAgentHost;
+}
+
 namespace headless {
 namespace {
 
@@ -67,6 +73,7 @@ HeadlessBrowserImpl::HeadlessBrowserImpl(
       options_(std::move(options)),
       browser_main_parts_(nullptr),
       default_browser_context_(nullptr),
+      agent_host_(nullptr),
       weak_ptr_factory_(this) {}
 
 HeadlessBrowserImpl::~HeadlessBrowserImpl() {}
@@ -133,6 +140,10 @@ void HeadlessBrowserImpl::set_browser_main_parts(
 }
 
 void HeadlessBrowserImpl::RunOnStartCallback() {
+  // We don't support the tethering domain on this agent host.
+  agent_host_ = content::DevToolsAgentHost::CreateForBrowser(
+      nullptr, content::DevToolsAgentHost::CreateServerSocketCallback());
+
   PlatformCreateWindow();
   on_start_callback_.Run(this);
   on_start_callback_ = base::Callback<void(HeadlessBrowser*)>();
@@ -200,6 +211,32 @@ HeadlessBrowserContext* HeadlessBrowserImpl::GetBrowserContextForId(
   return find_it->second.get();
 }
 
+HeadlessDevToolsTarget* HeadlessBrowserImpl::GetDevToolsTarget() {
+  return agent_host_ ? this : nullptr;
+}
+
+bool HeadlessBrowserImpl::AttachClient(HeadlessDevToolsClient* client) {
+  DCHECK(agent_host_);
+  return HeadlessDevToolsClientImpl::From(client)->AttachToHost(
+      agent_host_.get());
+}
+
+void HeadlessBrowserImpl::ForceAttachClient(HeadlessDevToolsClient* client) {
+  DCHECK(agent_host_);
+  HeadlessDevToolsClientImpl::From(client)->ForceAttachToHost(
+      agent_host_.get());
+}
+
+void HeadlessBrowserImpl::DetachClient(HeadlessDevToolsClient* client) {
+  DCHECK(agent_host_);
+  HeadlessDevToolsClientImpl::From(client)->DetachFromHost(agent_host_.get());
+}
+
+bool HeadlessBrowserImpl::IsAttached() {
+  DCHECK(agent_host_);
+  return agent_host_->IsAttached();
+}
+
 void RunChildProcessIfNeeded(int argc, const char** argv) {
   base::CommandLine::Init(argc, argv);
   const base::CommandLine& command_line(