[DevTools] Cleanup DevToolsTarget and DevToolsManagerDelegate after moving to devtools_discovery.

components/devtools_discovery/devtools_discovery_manager.h

 // 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.
 
 #ifndef COMPONENTS_DEVTOOLS_DISCOVERY_DEVTOOLS_DISCOVERY_MANAGER_H_
 #define COMPONENTS_DEVTOOLS_DISCOVERY_DEVTOOLS_DISCOVERY_MANAGER_H_
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "components/devtools_discovery/devtools_target_descriptor.h"
 
 namespace devtools_discovery {
 
 class DevToolsDiscoveryManager {
  public:
   class Provider {
    public:
     virtual ~Provider() {}
+
+    // Caller takes ownership of created descriptors.
     virtual DevToolsTargetDescriptor::List GetDescriptors() = 0;
   };
 
   using CreateCallback = base::Callback<
       scoped_ptr<DevToolsTargetDescriptor>(const GURL& url)>;
 
   // Returns single instance of this class. The instance is destroyed on the
   // browser main loop exit so this method MUST NOT be called after that point.
   static DevToolsDiscoveryManager* GetInstance();
 
   void AddProvider(scoped_ptr<Provider> provider);
   void SetCreateCallback(const CreateCallback& callback);
 
+  // Caller takes ownership of created descriptors.
   DevToolsTargetDescriptor::List GetDescriptors();
   scoped_ptr<DevToolsTargetDescriptor> CreateNew(const GURL& url);
 
  private:
   friend struct DefaultSingletonTraits<DevToolsDiscoveryManager>;
 
   DevToolsDiscoveryManager();
   ~DevToolsDiscoveryManager();
   DevToolsTargetDescriptor::List GetDescriptorsFromProviders();
 
   std::vector<Provider*> providers_;
   CreateCallback create_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(DevToolsDiscoveryManager);
 };
 
 }  // namespace devtools_discovery
 
 #endif  // COMPONENTS_DEVTOOLS_DISCOVERY_DEVTOOLS_DISCOVERY_MANAGER_H_