Upstream most of the iOS WebUI support in ios/web/

ios/web/webui/url_data_source_ios_impl.h

+// Copyright 2014 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 IOS_INTERNAL_WEB_WEBUI_URL_DATA_SOURCE_IMPL_IOS_H_
+#define IOS_INTERNAL_WEB_WEBUI_URL_DATA_SOURCE_IMPL_IOS_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/sequenced_task_runner_helpers.h"
+#include "ios/web/webui/url_data_manager_ios.h"
+
+namespace base {
+class RefCountedMemory;
+}
+
+namespace web {
+class URLDataManagerIOSBackend;
+class URLDataSourceIOS;
+class URLDataSourceIOSImpl;
+
+// Trait used to handle deleting a URLDataSourceIOS. Deletion happens on the UI
+// thread.
+//
+// Implementation note: the normal shutdown sequence is for the UI loop to stop
+// pumping events then the IO loop and thread are stopped. When the
+// URLDataSourceIOSs are no longer referenced (which happens when IO thread
+// stops) they get added to the UI message loop for deletion. But because the
+// UI loop has stopped by the time this happens the URLDataSourceIOSs would be
+// leaked.
+//
+// To make sure URLDataSourceIOSs are properly deleted URLDataManagerIOS
+// manages deletion of the URLDataSourceIOSs.  When a URLDataSourceIOS is no
+// longer referenced it is added to |data_sources_| and a task is posted to the
+// UI thread to handle the actual deletion. During shutdown |DeleteDataSources|
+// is invoked so that all pending URLDataSourceIOSs are properly deleted.
+struct DeleteURLDataSourceIOS {
+  static void Destruct(const URLDataSourceIOSImpl* data_source) {
+    URLDataManagerIOS::DeleteDataSource(data_source);
+  }
+};
+
+// A URLDataSourceIOS is an object that can answer requests for data
+// asynchronously. URLDataSourceIOSs are collectively owned with refcounting
+// smart pointers and should never be deleted on the IO thread, since their
+// calls are handled almost always on the UI thread and there's a possibility
+// of a data race.  The |DeleteDataSource| trait above is used to enforce this.
+class URLDataSourceIOSImpl
+    : public base::RefCountedThreadSafe<URLDataSourceIOSImpl,
+                                        DeleteURLDataSourceIOS> {
+ public:
+  // See source_name_ below for docs on that parameter. Takes ownership of
+  // |source|.
+  URLDataSourceIOSImpl(const std::string& source_name,
+                       URLDataSourceIOS* source);
+
+  // Report that a request has resulted in the data |bytes|.
+  // If the request can't be satisfied, pass NULL for |bytes| to indicate
+  // the request is over.
+  virtual void SendResponse(int request_id, base::RefCountedMemory* bytes);
+
+  const std::string& source_name() const { return source_name_; }
+  URLDataSourceIOS* source() const { return source_.get(); }
+
+ protected:
+  virtual ~URLDataSourceIOSImpl();
+
+ private:
+  friend class URLDataManagerIOS;
+  friend class URLDataManagerIOSBackend;
+  friend class base::DeleteHelper<URLDataSourceIOSImpl>;
+
+  // SendResponse invokes this on the IO thread. Notifies the backend to
+  // handle the actual work of sending the data.
+  virtual void SendResponseOnIOThread(
+      int request_id,
+      scoped_refptr<base::RefCountedMemory> bytes);
+
+  // The name of this source.
+  // E.g., for favicons, this could be "favicon", which results in paths for
+  // specific resources like "favicon/34" getting sent to this source.
+  const std::string source_name_;
+
+  // This field is set and maintained by URLDataManagerIOSBackend. It is set
+  // when the DataSource is added, and unset if the DataSource is removed. A
+  // DataSource can be removed in two ways: the URLDataManagerIOSBackend is
+  // deleted, or another DataSource is registered with the same name. backend_
+  // should only be accessed on the IO thread. This reference can't be via a
+  // scoped_refptr else there would be a cycle between the backend and data
+  // source.
+  URLDataManagerIOSBackend* backend_;
+
+  scoped_ptr<URLDataSourceIOS> source_;
+};
+
+}  // namespace web
+
+#endif  // IOS_INTERNAL_WEB_WEBUI_URL_DATA_SOURCE_IMPL_IOS_H_