DevTools: retain DTAH in all the targets to match their life time.

content/public/browser/devtools_manager_delegate.cc

Index: content/public/browser/devtools_manager_delegate.cc
diff --git a/content/public/browser/devtools_manager_delegate.cc b/content/public/browser/devtools_manager_delegate.cc
index e4de444bdcf0d6941bfb28be0bb14968b4b41acc..ae78127c47e39d4d5781d33d068542b44de7a7eb 100644
--- a/content/public/browser/devtools_manager_delegate.cc
+++ b/content/public/browser/devtools_manager_delegate.cc
@@ -23,11 +23,14 @@ std::string DevToolsManagerDelegate::GetTargetDescription(
   return std::string();
 }
 
-bool DevToolsManagerDelegate::DiscoverTargets(
-    const DevToolsAgentHost::DiscoveryCallback& callback) {
+bool DevToolsManagerDelegate::CanDiscoverTargets() {
   return false;
 }
 
+DevToolsAgentHost::List DevToolsManagerDelegate::DiscoverTargets() {
+  return DevToolsAgentHost::List();
+}
+
 scoped_refptr<DevToolsAgentHost> DevToolsManagerDelegate::CreateNewTarget(
     const GURL& url) {
   return nullptr;