Use file handles to interact with utility process.

chrome/browser/printing/pdf_to_emf_converter.cc

 // 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.
 
 #include "chrome/browser/printing/pdf_to_emf_converter.h"
 
-#include "base/bind_helpers.h"
-#include "base/cancelable_callback.h"
 #include "base/files/file.h"
 #include "base/files/file_util.h"
-#include "base/files/scoped_temp_dir.h"
 #include "base/logging.h"
 #include "chrome/common/chrome_utility_messages.h"
 #include "chrome/common/chrome_utility_printing_messages.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/child_process_data.h"
 #include "content/public/browser/utility_process_host.h"
 #include "content/public/browser/utility_process_host_client.h"
 #include "printing/emf_win.h"
-#include "printing/page_range.h"
 #include "printing/pdf_render_settings.h"
 
 namespace printing {
 
 namespace {
 
 using content::BrowserThread;
 
-class FileHandlers
-    : public base::RefCountedThreadSafe<FileHandlers,
-                                        BrowserThread::DeleteOnFileThread> {
+class PdfToEmfConverterImpl;
+
+typedef scoped_ptr<base::File, BrowserThread::DeleteOnFileThread> TempFilePtr;

[Lei Zhang, 2014/09/16 03:36:54]

Maybe rename TempFilePtr to ScopedTempFile?

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+
+// Wrapper for Emf to keep only file handle in memory, and load actual data only
+// on playback. |InitFromFile| can play metafile directly from disk, but it

[Lei Zhang, 2014/09/16 03:36:54]

nit: |InitFromFile| -> Emf::InitFromFile()

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+// can't open file handles. We need file handles to reliably delete temporary
+// files, and to efficiently interact with sandbox process.

[Lei Zhang, 2014/09/16 03:36:54]

nit: sandbox -> utility?

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+class LazyEmf : public MetafilePlayer {
  public:
-  FileHandlers() {}
-
-  void Init(base::RefCountedMemory* data);
-  bool IsValid();
-
-  base::FilePath GetEmfPath() const {
-    return temp_dir_.path().AppendASCII("output.emf");
-  }
-
-  base::FilePath GetEmfPagePath(int page_number) const {
-    return GetEmfPath().InsertBeforeExtensionASCII(
-        base::StringPrintf(".%d", page_number));
-  }
-
-  base::FilePath GetPdfPath() const {
-    return temp_dir_.path().AppendASCII("input.pdf");
-  }
-
-  IPC::PlatformFileForTransit GetPdfForProcess(base::ProcessHandle process) {
-    DCHECK(pdf_file_.IsValid());
-    IPC::PlatformFileForTransit transit =
-        IPC::TakeFileHandleForProcess(pdf_file_.Pass(), process);
-    return transit;
-  }
-
-  const base::FilePath& GetBasePath() const {
-    return temp_dir_.path();
-  }
+  explicit LazyEmf(TempFilePtr file) : file_(file.Pass()) {}
+  virtual ~LazyEmf() { Close(); }
+
+  virtual bool SafePlayback(HDC hdc) const OVERRIDE;
+  virtual bool SaveTo(base::File* file) const OVERRIDE;
 
  private:
-  friend struct BrowserThread::DeleteOnThread<BrowserThread::FILE>;
-  friend class base::DeleteHelper<FileHandlers>;
-
-  ~FileHandlers() { DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE)); }
-
-  base::ScopedTempDir temp_dir_;
-  base::File pdf_file_;
-};
-
-void FileHandlers::Init(base::RefCountedMemory* data) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-
-  if (!temp_dir_.CreateUniqueTempDir()) {
-    return;
-  }
-
-  pdf_file_.Initialize(GetPdfPath(),
-                       base::File::FLAG_CREATE_ALWAYS | base::File::FLAG_WRITE |
-                           base::File::FLAG_READ |
-                           base::File::FLAG_DELETE_ON_CLOSE);
-  if (static_cast<int>(data->size()) !=
-      pdf_file_.WriteAtCurrentPos(data->front_as<char>(), data->size())) {
-    pdf_file_.Close();
-    return;
-  }
-  pdf_file_.Seek(base::File::FROM_BEGIN, 0);
-  pdf_file_.Flush();
-}
-
-bool FileHandlers::IsValid() {
-  return pdf_file_.IsValid();
-}
-
-// Modification of Emf to keep references to |FileHandlers|.
-// |FileHandlers| must be deleted after the last metafile is closed because
-// Emf holds files locked.
-// Ideally we want to use FLAG_DELETE_ON_CLOSE, but it requires large changes.
-// It's going to be done for crbug.com/408184
-class TempEmf : public Emf {
- public:
-  explicit TempEmf(const scoped_refptr<FileHandlers>& files) : files_(files) {}
-  virtual ~TempEmf() {}
-
-  virtual bool SafePlayback(HDC hdc) const OVERRIDE {
-    bool result = Emf::SafePlayback(hdc);
-    TempEmf* this_mutable = const_cast<TempEmf*>(this);
-    // TODO(vitalybuka): Fix destruction of metafiles. For some reasons
-    // instances of Emf are not deleted. crbug.com/411683
-    // |files_| must be released as soon as possible to guarantee deletion.
-    // It's know that this Emf file is going to be played just once to
-    // a printer. So just release files here.
-    this_mutable->Close();
-    this_mutable->files_ = NULL;
-    return result;
-  }
-
- private:
-  scoped_refptr<FileHandlers> files_;
-  DISALLOW_COPY_AND_ASSIGN(TempEmf);
+  void Close() const;
+  bool LoadEmf(Emf* emf) const;
+
+  mutable TempFilePtr file_;  // Mutable because of consts in base class.
+  DISALLOW_COPY_AND_ASSIGN(LazyEmf);
 };
 
 // Converts PDF into EMF.
 // Class uses 3 threads: UI, IO and FILE.
 // Internal workflow is following:
 // 1. Create instance on the UI thread. (files_, settings_,)
-// 2. Create file on the FILE thread.
+// 2. Create pdf file on the FILE thread.
 // 3. Start utility process and start conversion on the IO thread.
-// 4. Run result callback on the UI thread.
-// 5. Instance is destroyed from any thread that has the last reference.
-// 6. FileHandlers destroyed on the FILE thread.
-//    This step posts |FileHandlers| to be destroyed on the FILE thread.
+// 4. Utility process returns page count.
+// 5. For each page:
+//   1. Clients requiquest page with file handle to temp file.

[Lei Zhang, 2014/09/16 03:36:54]

typo

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+//   2. Utility converts the page, save it to the file and reply.
+
 // All these steps work sequentially, so no data should be accessed
 // simultaneously by several threads.
 class PdfToEmfUtilityProcessHostClient
     : public content::UtilityProcessHostClient {
  public:
-  explicit PdfToEmfUtilityProcessHostClient(
-      const printing::PdfRenderSettings& settings);
-
-  void Convert(base::RefCountedMemory* data,
-               const PdfToEmfConverter::ResultCallback& callback);
+  PdfToEmfUtilityProcessHostClient(
+      base::WeakPtr<PdfToEmfConverterImpl> converter,
+      const PdfRenderSettings& settings);
+
+  void Start(const scoped_refptr<base::RefCountedMemory>& data,
+             const PdfToEmfConverter::StartCallback& start_callback);
+
+  void GetPage(int page_number,
+               const PdfToEmfConverter::GetPageCallback& get_page_callback);
+
+  void Stop();
 
   // UtilityProcessHostClient implementation.
   virtual void OnProcessCrashed(int exit_code) OVERRIDE;
+  virtual void OnProcessLaunchFailed() OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
  private:
   virtual ~PdfToEmfUtilityProcessHostClient();
 
+  bool Send(IPC::Message* msg);
+
   // Message handlers.
   void OnProcessStarted();
-  void OnSucceeded(const std::vector<printing::PageRange>& page_ranges,
-                   double scale_factor);
+  void OnPageCount(int page_count);
+  void OnPageDone(bool success, double scale_factor);
+
   void OnFailed();
-
-  void RunCallback(const std::vector<printing::PageRange>& page_ranges,
-                   double scale_factor);
-
-  void StartProcessOnIOThread();
-
-  void RunCallbackOnUIThread(
-      const std::vector<printing::PageRange>& page_ranges,
-      double scale_factor);
-  void OnFilesReadyOnUIThread();
-
-  scoped_refptr<FileHandlers> files_;
-  printing::PdfRenderSettings settings_;
-  PdfToEmfConverter::ResultCallback callback_;
+  void OnTempPdfReady(TempFilePtr pdf);
+  void OnTempEmfReady(int page_number, TempFilePtr emf);
+
+  // Used to suppress callbacks after PdfToEmfConverterImpl is deleted.
+  base::WeakPtr<PdfToEmfConverterImpl> converter_;
+  PdfRenderSettings settings_;
+  scoped_refptr<base::RefCountedMemory> data_;
+
+  // Document loaded callback.
+  PdfToEmfConverter::StartCallback start_callback_;
+
+  // Process host for IPC.
   base::WeakPtr<content::UtilityProcessHost> utility_process_host_;
 
+  std::map<int, std::pair<PdfToEmfConverter::GetPageCallback, TempFilePtr> >

[Lei Zhang, 2014/09/16 03:36:54]

document what the key is.

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+      get_page_callbacks_;
+
   DISALLOW_COPY_AND_ASSIGN(PdfToEmfUtilityProcessHostClient);
 };
 
+class PdfToEmfConverterImpl : public PdfToEmfConverter {
+ public:
+  PdfToEmfConverterImpl();
+
+  virtual ~PdfToEmfConverterImpl();
+
+  virtual void Start(const scoped_refptr<base::RefCountedMemory>& data,
+                     const PdfRenderSettings& conversion_settings,
+                     const StartCallback& start_callback) OVERRIDE;
+
+  virtual void GetPage(int page_number,
+                       const GetPageCallback& get_page_callback) OVERRIDE;
+
+  // Helps to cancel callbacks if this object is destroyed.
+  void RunCallback(const base::Closure& callback);
+
+ private:
+  scoped_refptr<PdfToEmfUtilityProcessHostClient> utility_client_;
+  base::WeakPtrFactory<PdfToEmfConverterImpl> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PdfToEmfConverterImpl);
+};
+
+TempFilePtr CreateTempFile() {
+  TempFilePtr file;
+  base::FilePath path;
+  if (!base::CreateTemporaryFile(&path))
+    return file.Pass();
+  file.reset(new base::File(path,
+                            base::File::FLAG_CREATE_ALWAYS |
+                                base::File::FLAG_WRITE | base::File::FLAG_READ |
+                                base::File::FLAG_DELETE_ON_CLOSE |
+                                base::File::FLAG_TEMPORARY));
+  if (!file->IsValid())
+    file.reset();
+  return file.Pass();
+}
+
+TempFilePtr CreateTempPdfFile(
+    const scoped_refptr<base::RefCountedMemory>& data) {
+  DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+
+  TempFilePtr pdf_file = CreateTempFile();
+  if (!pdf_file ||
+      static_cast<int>(data->size()) !=
+          pdf_file->WriteAtCurrentPos(data->front_as<char>(), data->size())) {
+    pdf_file.reset();
+  }
+  pdf_file->Seek(base::File::FROM_BEGIN, 0);
+  return pdf_file.Pass();
+}
+
+bool LazyEmf::SafePlayback(HDC hdc) const {
+  Emf emf;
+  bool result = LoadEmf(&emf) && emf.SafePlayback(hdc);
+  // TODO(vitalybuka): Fix destruction of metafiles. For some reasons
+  // instances of Emf are not deleted. crbug.com/411683
+  // It's known that the Emf going to be played just once to a printer. So just
+  // release file here.
+  Close();
+  return result;
+}
+
+bool LazyEmf::SaveTo(base::File* file) const {
+  Emf emf;
+  return LoadEmf(&emf) && emf.SaveTo(file);
+}
+
+void LazyEmf::Close() const {
+  file_.reset();
+}
+
+bool LazyEmf::LoadEmf(Emf* emf) const {
+  file_->Seek(base::File::FROM_BEGIN, 0);
+  int64 size = file_->GetLength();
+  if (size <= 0)
+    return false;
+  std::vector<char> data(size);
+  if (file_->ReadAtCurrentPos(data.data(), data.size()) != size)
+    return false;
+  return emf->InitFromData(data.data(), data.size());
+}
+
 PdfToEmfUtilityProcessHostClient::PdfToEmfUtilityProcessHostClient(
-    const printing::PdfRenderSettings& settings)
-    : settings_(settings) {}
+    base::WeakPtr<PdfToEmfConverterImpl> converter,
+    const PdfRenderSettings& settings)
+    : converter_(converter), settings_(settings) {
+}
 
 PdfToEmfUtilityProcessHostClient::~PdfToEmfUtilityProcessHostClient() {
 }
 
-void PdfToEmfUtilityProcessHostClient::Convert(
-    base::RefCountedMemory* data,
-    const PdfToEmfConverter::ResultCallback& callback) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  callback_ = callback;
-  CHECK(!files_.get());
-  files_ = new FileHandlers();
-  BrowserThread::PostTaskAndReply(
+void PdfToEmfUtilityProcessHostClient::Start(
+    const scoped_refptr<base::RefCountedMemory>& data,
+    const PdfToEmfConverter::StartCallback& start_callback) {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(BrowserThread::IO,
+                            FROM_HERE,
+                            base::Bind(&PdfToEmfUtilityProcessHostClient::Start,
+                                       this,
+                                       data,
+                                       start_callback));
+    return;
+  }
+  data_ = data;
+  start_callback_ = start_callback;
+
+  // NOTE: This process _must_ be sandboxed, otherwise the pdf dll will load
+  // gdiplus.dll, change how rendering happens, and not be able to correctly
+  // generate when sent to a metafile DC.
+  utility_process_host_ =
+      content::UtilityProcessHost::Create(
+          this, base::MessageLoop::current()->message_loop_proxy())
+          ->AsWeakPtr();
+  if (!utility_process_host_)
+    return OnFailed();
+  Send(new ChromeUtilityMsg_StartupPing);
+}
+
+void PdfToEmfUtilityProcessHostClient::GetPage(
+    int page_number,
+    const PdfToEmfConverter::GetPageCallback& get_page_callback) {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(
+        BrowserThread::IO,
+        FROM_HERE,
+        base::Bind(&PdfToEmfUtilityProcessHostClient::GetPage,
+                   this,
+                   page_number,
+                   get_page_callback));
+    return;
+  }
+
+  bool new_request =
+      get_page_callbacks_.insert(std::make_pair(
+                                     page_number,
+                                     std::make_pair(get_page_callback,
+                                                    TempFilePtr()))).second;
+  DCHECK(new_request) << "Multiple requests for the same page";
+  if (!new_request || !utility_process_host_)
+    return OnFailed();
+
+  BrowserThread::PostTaskAndReplyWithResult(
       BrowserThread::FILE,
       FROM_HERE,
-      base::Bind(&FileHandlers::Init, files_, make_scoped_refptr(data)),
-      base::Bind(&PdfToEmfUtilityProcessHostClient::OnFilesReadyOnUIThread,
-                 this));
+      base::Bind(&CreateTempFile),
+      base::Bind(&PdfToEmfUtilityProcessHostClient::OnTempEmfReady,

[Lei Zhang, 2014/09/16 03:36:54]

Can you move the OnTempEmfReady() impl to be right below here, so it's easier to
follow the "success" path?

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+                 this,
+                 page_number));
+}
+
+void PdfToEmfUtilityProcessHostClient::Stop() {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(
+        BrowserThread::IO,
+        FROM_HERE,
+        base::Bind(&PdfToEmfUtilityProcessHostClient::Stop, this));
+    return;
+  }
+  Send(new ChromeUtilityMsg_RenderPDFPagesToMetafiles_Stop());
 }
 
 void PdfToEmfUtilityProcessHostClient::OnProcessCrashed(int exit_code) {
   OnFailed();
 }
 
+void PdfToEmfUtilityProcessHostClient::OnProcessLaunchFailed() {
+  OnFailed();
+}
+
 bool PdfToEmfUtilityProcessHostClient::OnMessageReceived(
   const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(PdfToEmfUtilityProcessHostClient, message)
     IPC_MESSAGE_HANDLER(ChromeUtilityHostMsg_ProcessStarted, OnProcessStarted)
     IPC_MESSAGE_HANDLER(
-        ChromeUtilityHostMsg_RenderPDFPagesToMetafiles_Succeeded, OnSucceeded)
-    IPC_MESSAGE_HANDLER(ChromeUtilityHostMsg_RenderPDFPagesToMetafile_Failed,
-                        OnFailed)
+        ChromeUtilityHostMsg_RenderPDFPagesToMetafiles_PageCount, OnPageCount)
+    IPC_MESSAGE_HANDLER(ChromeUtilityHostMsg_RenderPDFPagesToMetafiles_PageDone,
+                        OnPageDone)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
+bool PdfToEmfUtilityProcessHostClient::Send(IPC::Message* msg) {
+  if (utility_process_host_)
+    return utility_process_host_->Send(msg);
+  delete msg;
+  return false;
+}
+
 void PdfToEmfUtilityProcessHostClient::OnProcessStarted() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  if (!utility_process_host_) {
-    RunCallbackOnUIThread(std::vector<printing::PageRange>(), 0.0);
-    return;
-  }
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!utility_process_host_)
+    return OnFailed();
 
   base::ProcessHandle process = utility_process_host_->GetData().handle;
-  utility_process_host_->Send(
-      new ChromeUtilityMsg_RenderPDFPagesToMetafiles(
-          files_->GetPdfForProcess(process),
-          files_->GetEmfPath(),
-          settings_,
-          std::vector<printing::PageRange>()));
-  utility_process_host_.reset();
-}
-
-void PdfToEmfUtilityProcessHostClient::OnSucceeded(
-    const std::vector<printing::PageRange>& page_ranges,
-    double scale_factor) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  RunCallback(page_ranges, scale_factor);
-}
-
-void PdfToEmfUtilityProcessHostClient::OnFailed() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  RunCallback(std::vector<printing::PageRange>(), 0.0);
-}
-
-void PdfToEmfUtilityProcessHostClient::OnFilesReadyOnUIThread() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  if (!files_->IsValid()) {
-    RunCallbackOnUIThread(std::vector<printing::PageRange>(), 0.0);
-    return;
-  }
-  BrowserThread::PostTask(
-      BrowserThread::IO,
+  scoped_refptr<base::RefCountedMemory> data = data_;
+  data_ = NULL;
+  BrowserThread::PostTaskAndReplyWithResult(
+      BrowserThread::FILE,
       FROM_HERE,
-      base::Bind(&PdfToEmfUtilityProcessHostClient::StartProcessOnIOThread,
-                 this));
-}
-
-void PdfToEmfUtilityProcessHostClient::StartProcessOnIOThread() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  utility_process_host_ =
-      content::UtilityProcessHost::Create(
-          this,
-          base::MessageLoop::current()->message_loop_proxy())->AsWeakPtr();
-  // NOTE: This process _must_ be sandboxed, otherwise the pdf dll will load
-  // gdiplus.dll, change how rendering happens, and not be able to correctly
-  // generate when sent to a metafile DC.
-  utility_process_host_->SetExposedDir(files_->GetBasePath());
-  utility_process_host_->Send(new ChromeUtilityMsg_StartupPing);
-}
-
-void PdfToEmfUtilityProcessHostClient::RunCallback(
-    const std::vector<printing::PageRange>& page_ranges,
-    double scale_factor) {
+      base::Bind(&CreateTempPdfFile, data),
+      base::Bind(&PdfToEmfUtilityProcessHostClient::OnTempPdfReady, this));

[Lei Zhang, 2014/09/16 03:36:54]

and move OnTempPdfReady to right after this.

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+}
+
+void PdfToEmfUtilityProcessHostClient::OnPageCount(int page_count) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (start_callback_.is_null())
+    return OnFailed();
+  BrowserThread::PostTask(BrowserThread::UI,
+                          FROM_HERE,
+                          base::Bind(&PdfToEmfConverterImpl::RunCallback,
+                                     converter_,
+                                     base::Bind(start_callback_, page_count)));
+  start_callback_.Reset();
+}
+
+void PdfToEmfUtilityProcessHostClient::OnPageDone(bool success,
+                                                  double scale_factor) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (get_page_callbacks_.empty())
+    return OnFailed();
+  scoped_ptr<LazyEmf> emf;
+  if (success)
+    emf.reset(new LazyEmf(get_page_callbacks_.begin()->second.second.Pass()));

[Lei Zhang, 2014/09/16 03:36:54]

nit: save the iterator from get_page_callbacks_.begin() and reuse it below
instead of writing get_page_callbacks_.begin() everywhere.

[Lei Zhang, 2014/09/16 03:36:54]

If you are using get_page_callbacks_.begin() here, then does that mean only one
callback can be in flight at any time? If so, why do we need the
|get_page_callbacks_| map?

Or are you taking advantage of the fact that begin() returns the lowest page #
due to std::map's sorting property, combined with the expectation that the
utility process convert pages in order? I'm guessing this is it, but it's not
quite obvious, so please add a comment.

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Actually this is a bug.
Works fine with current client, but if GetPage(2), GetPage(1) would fail.
Changed to queue

On 2014/09/16 03:36:54, Lei Zhang wrote:

   BrowserThread::PostTask(
       BrowserThread::UI,
       FROM_HERE,
-      base::Bind(&PdfToEmfUtilityProcessHostClient::RunCallbackOnUIThread,
-                 this,
-                 page_ranges,
-                 scale_factor));
-}
-
-void PdfToEmfUtilityProcessHostClient::RunCallbackOnUIThread(
-    const std::vector<printing::PageRange>& page_ranges,
-    double scale_factor) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  ScopedVector<MetafilePlayer> pages;
-  std::vector<printing::PageRange>::const_iterator iter;
-  for (iter = page_ranges.begin(); iter != page_ranges.end(); ++iter) {
-    for (int page_number = iter->from; page_number <= iter->to; ++page_number) {
-      scoped_ptr<TempEmf> metafile(new TempEmf(files_));
-      if (!metafile->InitFromFile(files_->GetEmfPagePath(page_number))) {
-        NOTREACHED() << "Invalid metafile";
-        metafile.reset();
-      }
-      pages.push_back(metafile.release());
-    }
-  }
-  files_ = NULL;
-  if (!callback_.is_null()) {
-    callback_.Run(scale_factor, &pages);
-    callback_.Reset();
-  }
-}
-
-class PdfToEmfConverterImpl : public PdfToEmfConverter {
- public:
-  PdfToEmfConverterImpl();
-
-  virtual ~PdfToEmfConverterImpl();
-
-  virtual void Start(base::RefCountedMemory* data,
-                     const printing::PdfRenderSettings& conversion_settings,
-                     const ResultCallback& callback) OVERRIDE;
-
- private:
-  scoped_refptr<PdfToEmfUtilityProcessHostClient> utility_client_;
-  base::CancelableCallback<ResultCallback::RunType> callback_;
-
-  DISALLOW_COPY_AND_ASSIGN(PdfToEmfConverterImpl);
-};
-
-PdfToEmfConverterImpl::PdfToEmfConverterImpl() {
+      base::Bind(&PdfToEmfConverterImpl::RunCallback,
+                 converter_,
+                 base::Bind(get_page_callbacks_.begin()->second.first,
+                            get_page_callbacks_.begin()->first,
+                            scale_factor,
+                            base::Passed(&emf))));
+  get_page_callbacks_.erase(get_page_callbacks_.begin());
+}
+
+void PdfToEmfUtilityProcessHostClient::OnFailed() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!start_callback_.is_null())
+    OnPageCount(0);
+  while (!get_page_callbacks_.empty())
+    OnPageDone(false, 0.0);
+  utility_process_host_.reset();
+}
+
+void PdfToEmfUtilityProcessHostClient::OnTempPdfReady(TempFilePtr pdf) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!utility_process_host_)
+    return OnFailed();
+  base::ProcessHandle process = utility_process_host_->GetData().handle;
+  Send(new ChromeUtilityMsg_RenderPDFPagesToMetafiles(
+      IPC::GetFileHandleForProcess(pdf->GetPlatformFile(), process, false),
+      settings_));
+}
+
+void PdfToEmfUtilityProcessHostClient::OnTempEmfReady(int page_number,
+                                                      TempFilePtr emf) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (!utility_process_host_ || get_page_callbacks_.count(page_number) != 1)

[Lei Zhang, 2014/09/16 03:36:54]

nit: ContainsKey(get_page_callbacks_, page_number)

[Vitaly Buka (NO REVIEWS), 2014/09/16 07:50:35]

Done.

+    return OnFailed();
+  base::ProcessHandle process = utility_process_host_->GetData().handle;
+  IPC::PlatformFileForTransit transit =
+      IPC::GetFileHandleForProcess(emf->GetPlatformFile(), process, false);
+  get_page_callbacks_[page_number].second = emf.Pass();
+  Send(new ChromeUtilityMsg_RenderPDFPagesToMetafiles_GetPage(page_number,
+                                                              transit));
+}
+
+PdfToEmfConverterImpl::PdfToEmfConverterImpl() : weak_ptr_factory_(this) {
 }
 
 PdfToEmfConverterImpl::~PdfToEmfConverterImpl() {
+  if (utility_client_)
+    utility_client_->Stop();
 }
 
 void PdfToEmfConverterImpl::Start(
-    base::RefCountedMemory* data,
-    const printing::PdfRenderSettings& conversion_settings,
-    const ResultCallback& callback) {
-  // Rebind cancelable callback to avoid calling callback if
-  // PdfToEmfConverterImpl is destroyed.
-  callback_.Reset(callback);
-  utility_client_ = new PdfToEmfUtilityProcessHostClient(conversion_settings);
-  utility_client_->Convert(data, callback_.callback());
+    const scoped_refptr<base::RefCountedMemory>& data,
+    const PdfRenderSettings& conversion_settings,
+    const StartCallback& start_callback) {
+  DCHECK(!utility_client_);
+  utility_client_ = new PdfToEmfUtilityProcessHostClient(
+      weak_ptr_factory_.GetWeakPtr(), conversion_settings);
+  utility_client_->Start(data, start_callback);
+}
+
+void PdfToEmfConverterImpl::GetPage(int page_number,
+                                    const GetPageCallback& get_page_callback) {
+  utility_client_->GetPage(page_number, get_page_callback);
+}
+
+void PdfToEmfConverterImpl::RunCallback(const base::Closure& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  callback.Run();
 }
 
 }  // namespace
 
+PdfToEmfConverter::~PdfToEmfConverter() {
+}
+
 // static
 scoped_ptr<PdfToEmfConverter> PdfToEmfConverter::CreateDefault() {
   return scoped_ptr<PdfToEmfConverter>(new PdfToEmfConverterImpl());
 }
 
 }  // namespace printing