Clean up of url data manager classes in content: move URLDataSourceImpl to its own file, move all t…

content/browser/webui/url_data_source_impl.cc

+// Copyright (c) 2012 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 "content/browser/webui/url_data_source_impl.h"
+
+#include "base/bind.h"
+#include "base/memory/ref_counted_memory.h"
+#include "base/string_util.h"
+#include "content/browser/webui/url_data_manager_backend.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/url_data_source.h"
+
+namespace content {
+
+URLDataSourceImpl::URLDataSourceImpl(const std::string& source_name,
+                                     URLDataSource* source)
+    : source_name_(source_name),
+      backend_(NULL),
+      source_(source) {
+}
+
+URLDataSourceImpl::~URLDataSourceImpl() {
+}
+
+void URLDataSourceImpl::SendResponse(
+    int request_id,
+    base::RefCountedMemory* bytes) {
+  // Take a ref-pointer on entry so byte->Release() will always get called.
+  scoped_refptr<base::RefCountedMemory> bytes_ptr(bytes);
+  if (URLDataManager::IsScheduledForDeletion(this)) {
+    // We're scheduled for deletion. Servicing the request would result in
+    // this->AddRef being invoked, even though the ref count is 0 and 'this' is
+    // about to be deleted. If the AddRef were allowed through, when 'this' is
+    // released it would be deleted again.
+    //
+    // This scenario occurs with DataSources that make history requests. Such
+    // DataSources do a history query in |StartDataRequest| and the request is
+    // live until the object is deleted (history requests don't up the ref
+    // count). This means it's entirely possible for the DataSource to invoke
+    // |SendResponse| between the time when there are no more refs and the time
+    // when the object is deleted.
+    return;
+  }
+  BrowserThread::PostTask(
+      BrowserThread::IO, FROM_HERE,
+      base::Bind(&URLDataSourceImpl::SendResponseOnIOThread, this, request_id,
+                 bytes_ptr));
+}
+
+void URLDataSourceImpl::SendResponseOnIOThread(
+    int request_id,
+    scoped_refptr<base::RefCountedMemory> bytes) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  if (backend_)
+    backend_->DataAvailable(request_id, bytes);
+}
+
+}  // namespace content