Added a test that currently is able to print to pdf.

chrome/browser/printing/print_preview_pdf_generated_browsertest.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 <cstdio>
+#include <iostream>
+#include <limits>
+#include <string>
+#include <vector>
+
+#include "base/file_util.h"
+#include "base/files/file.h"
+#include "base/files/file_path.h"
+#include "base/files/scoped_temp_dir.h"
+#include "base/format_macros.h"
+#include "base/logging.h"
+#include "base/md5.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/numerics/safe_conversions.h"
+#include "base/path_service.h"
+#include "base/run_loop.h"
+#include "base/scoped_native_library.h"
+#include "base/strings/string16.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "chrome/app/chrome_command_ids.h"
+#include "chrome/browser/net/referrer.h"
+#include "chrome/browser/printing/print_preview_dialog_controller.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_commands.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
+#include "chrome/browser/ui/webui/print_preview/print_preview_handler.h"
+#include "chrome/browser/ui/webui/print_preview/print_preview_ui.h"
+#include "chrome/browser/ui/webui/print_preview/sticky_settings.h"
+#include "chrome/common/chrome_paths.h"
+#include "chrome/common/print_messages.h"
+#include "chrome/common/url_constants.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_ui_message_handler.h"
+#include "content/public/common/page_transition_types.h"
+#include "content/public/test/browser_test_utils.h"
+#include "content/public/test/test_navigation_observer.h"
+#include "content/public/test/test_utils.h"
+#include "net/base/filename_util.h"
+#include "printing/pdf_render_settings.h"
+#include "printing/units.h"
+#include "ui/events/keycodes/keyboard_codes.h"
+#include "ui/gfx/codec/png_codec.h"
+#include "ui/gfx/geometry/rect.h"
+#include "url/gurl.h"
+#include "ipc/ipc_message_macros.h"
+
+#if defined(OS_POSIX)
+#define STDIN_STREAM std::cin
+#elif defined(OS_WIN)
+#define STDIN_STREAM std::wcin
+#endif
+
+using content::WebContents;
+using content::WebContentsObserver;
+
+// Message refers to the 'UILoaded' message from print_preview.js.
+// It gets sent either from onPreviewGenerationDone or from
+// onManipulateSettings_() in print_preview.js
+enum State {
+  // Waiting for the first message so the program can select Save as PDF
+  kWaitingToSendSaveAsPdf = 0,
+  // Waiting for the second message so the test can set the layout
+  kWaitingToSendLayoutSettings = 1,
+  // Waiting for the third message so the test can set the page numbers
+  kWaitingToSendPageNumbers = 2,
+  // Waiting for the forth message so the test can set the headers checkbox
+  kWaitingToSendHeadersAndFooters = 3,
+  // Waiting for the fifth message so the test can set the background checkbox
+  kWaitingToSendBackgroundColorsAndImages = 4,
+  // Waiting for the sixth message so the test can set the margins combobox
+  kWaitingToSendMargins = 5,
+  // Waiting for the final message so the program can save to PDF.
+  kWaitingForFinalMessage = 6,
+};
+
+struct PrintPreviewSettings {
+  PrintPreviewSettings(bool is_portrait,
+                       std::string page_numbers,
+                       bool headers_and_footers,
+                       bool background_colors_and_images,
+                       printing::MarginType margins,
+                       bool is_already_pdf)
+      : is_portrait(is_portrait),
+        page_numbers(page_numbers),
+        headers_and_footers(headers_and_footers),
+        background_colors_and_images(background_colors_and_images),
+        margins(margins),
+        is_already_pdf(is_already_pdf) {}
+
+  bool is_portrait;
+  std::string page_numbers;
+  bool headers_and_footers;
+  bool background_colors_and_images;
+  printing::MarginType margins;
+  bool is_already_pdf;
+};
+
+// Observes the print preview webpage. Once it observes the
+// PreviewPageCount message, will send a sequence of commands
+// to the print preview dialog and change the settings of the
+// preview dialog.
+class PrintPreviewObserver : public WebContentsObserver {
+ public:
+  PrintPreviewObserver(WebContents* dialog,
+                       Browser* browser)
+      : WebContentsObserver(dialog),
+        browser_(browser),
+        state_(kWaitingToSendSaveAsPdf) {}
+
+  virtual ~PrintPreviewObserver() {}
+
+  // Sets closure for the observer so that it can end the loop.
+  void set_quit_closure(const base::Closure &closure) {
+    closure_ = closure;
+  }
+
+  // Actually stops the message_loop so that the test can proceed.
+  void EndLoop() {
+    base::MessageLoop::current()->PostTask(FROM_HERE, closure_);
+  }
+
+  // This method must always return false. If it ever returns true,
+  // it will cause the test to hang. This is because the
+  // PrintPreviewMessageHandler should still handle all of the messages to
+  // progress the print preview process.
+  bool OnMessageReceived(const IPC::Message& message) OVERRIDE {
+    IPC_BEGIN_MESSAGE_MAP(PrintPreviewObserver, message)
+      IPC_MESSAGE_HANDLER(PrintHostMsg_DidGetPreviewPageCount,
+                          OnDidGetPreviewPageCount)
+      IPC_MESSAGE_UNHANDLED(break;)

[Dan Beam, 2014/07/08 04:25:13]

i still don't love that there's a break; here because it assumes the code
generated by this macro is a switch or a loop, but i guess "return false;"
assumes it's not in a ctor...

[ivandavid, 2014/07/08 23:24:21]

I decided to remove it. It doesn't affect my test, so it seems to be OK. I still
just return false at the end.

+    IPC_END_MESSAGE_MAP();
+    return false;
+  }
+
+  // Gets the web contents for the print preview dialog so that
+  // the UI and other elements can be accessed.
+  WebContents* GetDialog() {
+    WebContents* tab = browser_->tab_strip_model()->GetActiveWebContents();
+    printing::PrintPreviewDialogController* dialog_controller =
+        printing::PrintPreviewDialogController::GetInstance();
+    WebContents* web_contents =
+        dialog_controller->GetPrintPreviewForContents(tab);
+    return web_contents;
+  }
+
+  // Gets the PrintPreviewUI so that certain elements can be accessed.
+  PrintPreviewUI* GetUI() {
+    return static_cast<PrintPreviewUI*>(
+        GetDialog()->GetWebUI()->GetController());
+  }
+
+  // Calls a javascript function that will change the print preview settings,
+  // such as the layout, the margins, page numbers, etc.
+  void ManipulatePreviewSettings() {
+    base::DictionaryValue script_argument;
+
+    if (state_ == kWaitingToSendSaveAsPdf) {
+      script_argument.SetBoolean("selectSaveAsPdfDestination", true);
+      state_ = settings_->is_already_pdf ?
+               kWaitingToSendPageNumbers :
+               kWaitingToSendLayoutSettings;
+    } else if (state_ == kWaitingToSendLayoutSettings) {
+      script_argument.SetBoolean("layoutSettings.portrait",
+                                  settings_->is_portrait);
+      state_ = kWaitingToSendPageNumbers;
+    } else if (state_ == kWaitingToSendPageNumbers) {
+      script_argument.SetString("pageRange", settings_->page_numbers);
+      state_ = settings_->is_already_pdf ?
+               kWaitingForFinalMessage :
+               kWaitingToSendHeadersAndFooters;
+    } else if (state_ == kWaitingToSendHeadersAndFooters) {
+      script_argument.SetBoolean("headersAndFooters",
+                                  settings_->headers_and_footers);
+      state_ = kWaitingToSendBackgroundColorsAndImages;
+    } else if (state_ == kWaitingToSendBackgroundColorsAndImages) {
+      script_argument.SetBoolean("backgroundColorsAndImages",
+                                   settings_->background_colors_and_images);
+      state_ = kWaitingToSendMargins;
+    } else if (state_ == kWaitingToSendMargins) {
+      script_argument.SetInteger("margins", settings_->margins);
+      state_ = kWaitingForFinalMessage;
+    } else if (state_ == kWaitingForFinalMessage) {
+      EndLoop();
+    }
+
+    DCHECK(!script_argument.empty());

[Dan Beam, 2014/07/08 04:25:13]

^ wouldn't this fail in the case of kWaitingForFinalMessage?

[ivandavid, 2014/07/08 23:24:21]

It should have, but it wasn't. I changed it to ASSERT_TRUE and now it works. I
have added a return after EndLoop() to account for this.

+    GetUI()->web_ui()->CallJavascriptFunction(
+        "onManipulateSettingsForTest", script_argument);
+  }
+
+  // Function to set the print preview settings and save them so they
+  // can be sent later. Currently only used in the constructor. Will be
+  // used when creating a test and take command line arguments.
+  // |page_numbers| is a comma separated page range.
+  //    Example: "1-5,9" will print pages 1 through 5 and page 9.
+  //    The pages specified must be less than or equal to the maximum
+  //    page number. An empty string seems to be valid input, however
+  //    further testing will be required to see if that is actually
+  //    true.
+  void SetPrintPreviewSettings(const PrintPreviewSettings& settings) {
+    settings_.reset(new PrintPreviewSettings(settings));
+  }
+
+ private:
+  class UIDoneLoadingMessageHandler : public content::WebUIMessageHandler {
+   public:
+    explicit UIDoneLoadingMessageHandler(PrintPreviewObserver* observer) {
+      observer_ = observer;

[Dan Beam, 2014/07/08 04:25:13]

nit:

  explicit UIDoneLoadingMessageHandler(PrintPreviewObserver* observer)
      : observer_(observer) {}

[ivandavid, 2014/07/08 23:24:21]

Dunno why I changed it to that.

Done.

+    }
+
+    virtual ~UIDoneLoadingMessageHandler() {}
+
+    // When a setting has been set succesfully, this is called and
+    // the observer_ is told to send the next setting to be set.
+    void HandleDone(const base::ListValue* /* args */) {
+      ASSERT_TRUE(observer_);
+      observer_->ManipulatePreviewSettings();
+    }
+
+    // Ends the test because a setting was not set successfully,
+    // therefore, the test shouldn't continue.
+    // TODO(ivandavid): Print out error message to give context.
+    void HandleFailure(const base::ListValue* /* args */) {
+      FAIL();
+    }
+
+    // Sets up this class to listen for the UILoadedForTest and
+    // UIFailedLoadingForTest messages. These messages are sent
+    // by print_preview.js. On UILoadedForTest, a settings has
+    // been successfully set and its effects on the pdf have been finalized.
+    // On UIFaieldLoadingForTest a setting has not been successfully set
+    // and the test should fail.
+    void RegisterMessages() OVERRIDE {
+      web_ui()->RegisterMessageCallback(
+          "UILoadedForTest",
+          base::Bind(&UIDoneLoadingMessageHandler::HandleDone,
+                     base::Unretained(this)));
+
+      web_ui()->RegisterMessageCallback(
+          "UIFailedLoadingForTest",
+          base::Bind(&UIDoneLoadingMessageHandler::HandleFailure,
+                     base::Unretained(this)));
+    }
+
+   private:
+    PrintPreviewObserver* observer_;

[Dan Beam, 2014/07/08 04:25:13]

nit:
  PrintPreviewObserver* observer_ const;

[ivandavid, 2014/07/08 23:24:21]

I'm not sure I can make observer_ const because the message handler calls
ManipulatePreviewSettings, which isn't const and can't be. So there is a problem
with const correctness here.

[Dan Beam, 2014/07/09 01:56:32]

  PrintPreviewObserver* observer_ const;

means that the pointer *itself* doesn't change (e.g. observer_ = NULL; inside
UIDoneLoadingMessageHandler wouldn't compile).

  const PrintPreviewObserver* observer_;

means observer_->CanOnlyCallConstMethods().

[ivandavid, 2014/07/09 19:58:21]

Ahh. I see. I think what we want is this however,
PrintPreviewObserver* const observer_;

The one you posted doesn't seem to compile, however what I wrote has the
behavior you described.

[Dan Beam, 2014/07/09 22:03:04]

yeah, my bad, ^ that one (sorry if this took a while to find out yourself...)

+
+    DISALLOW_COPY_AND_ASSIGN(UIDoneLoadingMessageHandler);
+  };
+
+  // Called when the observer gets the IPC message stating that the
+  // page count is ready.
+  // Due to forward declaration problem, the definition of the function
+  // must be separated from the declaration.
+  void OnDidGetPreviewPageCount(
+      const PrintHostMsg_DidGetPreviewPageCount_Params &params) {
+    WebContents* web_contents = GetDialog();
+    PrintPreviewUI* ui = GetUI();
+    ASSERT_TRUE(ui);
+    ASSERT_TRUE(ui->web_ui());
+    Observe(web_contents);
+    ASSERT_TRUE(web_contents);
+    ui->web_ui()->AddMessageHandler(new UIDoneLoadingMessageHandler(this));
+    ui->web_ui()->CallJavascriptFunction("onEnableManipulateSettingsForTest");
+  }
+
+  void DidCloneToNewWebContents(WebContents* old_web_contents,
+                                WebContents* new_web_contents) OVERRIDE {
+    Observe(new_web_contents);
+  }
+
+  void WebContentsDestroyed() OVERRIDE {
+    EndLoop();
+  }
+
+  Browser* browser_;
+  base::Closure closure_;
+  scoped_ptr<PrintPreviewSettings> settings_;
+  State state_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrintPreviewObserver);
+};
+
+class PrintPreviewPdfGeneratedBrowserTest : public InProcessBrowserTest {
+ public:
+  PrintPreviewPdfGeneratedBrowserTest() {}
+  virtual ~PrintPreviewPdfGeneratedBrowserTest() {}
+
+  // Navigates to the web page given, then initiates print preview
+  // and waits for all the settings to be set.
+  void NavigateAndPreview(const base::FilePath::StringType& file_name,
+                          PrintPreviewSettings settings) {
+    print_preview_observer_->SetPrintPreviewSettings(settings);
+    base::FilePath path(file_name);
+    GURL gurl = net::FilePathToFileURL(path);
+
+    ui_test_utils::NavigateToURL(browser(), gurl);
+
+    base::RunLoop loop;
+    print_preview_observer_->set_quit_closure(loop.QuitClosure());
+    chrome::Print(browser());
+    loop.Run();
+  }
+
+  // Prints the webpage to pdf, after the settings have been set.
+  void Print() {
+    ASSERT_FALSE(pdf_file_save_path_.empty());
+    base::RunLoop loop;
+    print_preview_observer_->set_quit_closure(loop.QuitClosure());
+    print_preview_observer_->GetUI()->handler_->FileSelected(
+        pdf_file_save_path_, 0, NULL);
+    loop.Run();
+  }
+
+  // Converts the pdf to a png file, so that the layout test can
+  // do an image diff on this image and a reference image.
+  void PdfToPng() {
+    // Get the library functions to get the pdf info.
+    base::ScopedNativeLibrary pdf_lib;
+    base::FilePath pdf_module_path;
+
+    ASSERT_TRUE(PathService::Get(chrome::FILE_PDF_PLUGIN, &pdf_module_path));
+    ASSERT_TRUE(base::PathExists(pdf_module_path));
+    pdf_lib.Reset(base::LoadNativeLibrary(pdf_module_path, NULL));
+
+    ASSERT_TRUE(pdf_lib.is_valid());
+    pdf_to_bitmap_func_ =
+        reinterpret_cast<PDFPageToBitmap>(
+            pdf_lib.GetFunctionPointer("RenderPDFPageToBitmap"));
+
+    pdf_doc_info_func_ =
+        reinterpret_cast<GetPDFDocInfoProc>(
+            pdf_lib.GetFunctionPointer("GetPDFDocInfo"));
+
+    pdf_page_size_func_ =
+        reinterpret_cast<GetPDFPageSizeByIndexProc>(
+            pdf_lib.GetFunctionPointer("GetPDFPageSizeByIndex"));
+
+    ASSERT_TRUE(pdf_to_bitmap_func_);
+    ASSERT_TRUE(pdf_doc_info_func_);
+    ASSERT_TRUE(pdf_page_size_func_);
+
+    std::string data;
+    int num_pages;
+    ASSERT_TRUE(base::ReadFileToString(pdf_file_save_path_, &data));
+    ASSERT_TRUE(pdf_doc_info_func_(data.data(),
+                                   data.size(),
+                                   &num_pages,
+                                   NULL));
+    std::vector<uint8_t> bitmap_data;
+    double min_width = std::numeric_limits<double>::max();
+    double total_height = 0;
+
+    for (int i = 0; i < num_pages; i++) {
+      double height, width;
+      ASSERT_TRUE(pdf_page_size_func_(
+          data.data(), data.size(), i, &width, &height));
+
+      height = printing::ConvertPointsToPixelDouble(height);
+      width = printing::ConvertPointsToPixelDouble(width);
+
+      bool autorotate = false;
+
+      if (height < width) {
+        double temp = height;
+        height = width;
+        width = temp;
+        autorotate = true;
+      }
+
+      total_height += height;
+
+      if (width < min_width)
+        min_width = width;
+
+      gfx::Rect rect(width, height);
+      printing::PdfRenderSettings settings(rect, 300, true);
+
+      // Detecting overflow. If a * b > max_size then there is overflow.
+      // So just check if a > max_size / b.
+      // Need to check both the cases in which GetArea() overflows and where
+      // GetArea() * 4 overflows. If the latter is just checked, then it is
+      // possible that if GetArea() overflows, the latter case will pass by
+      // virtue of it overflowing to a value of 1 or something like that.
+      // Also, for the first comparison, height is promoted to size_t.
+      size_t max_size = std::numeric_limits<size_t>::max();
+      if (static_cast<size_t>(settings.area().size().width()) >
+          max_size / settings.area().size().height() ||
+          static_cast<size_t>(settings.area().size().GetArea()) >
+          max_size / 4) {
+        LOG(ERROR) << "OVERFLOW DETECTED: IMAGE DIMENSIONS ARE TOO LARGE!";
+        FAIL();
+      }
+
+      std::vector<uint8_t> page_bitmap_data(
+          4 * settings.area().size().GetArea());
+
+      ASSERT_TRUE(pdf_to_bitmap_func_(data.data(),
+                                      data.size(),
+                                      i,
+                                      page_bitmap_data.data(),
+                                      settings.area().size().width(),
+                                      settings.area().size().height(),
+                                      settings.dpi(),
+                                      settings.dpi(),
+                                      autorotate));
+
+      bitmap_data.insert(bitmap_data.end(),
+                         page_bitmap_data.begin(),
+                         page_bitmap_data.end());
+    }
+
+    std::string hash_input(bitmap_data.begin(), bitmap_data.end());
+    base::MD5Sum(static_cast<void*>(const_cast<char*>(hash_input.data())),
+                 hash_input.size(),
+                 &hash_);
+
+    gfx::Rect png_rect(min_width, total_height);
+
+    std::string comment_title("tEXtchecksum\x00");
+    gfx::PNGCodec::Comment hash_comment(
+        comment_title,
+        base::MD5DigestToBase16(hash_));
+
+    std::vector<gfx::PNGCodec::Comment> comments;
+    comments.push_back(hash_comment);
+
+    ASSERT_TRUE(
+        gfx::PNGCodec::Encode(static_cast<unsigned char*>(
+            bitmap_data.data()),
+            gfx::PNGCodec::FORMAT_BGRA,
+            png_rect.size(),
+            png_rect.size().width() * sizeof(uint32_t),
+            false,
+            comments,
+            &output_));
+  }
+
+  // Sends the png image to the layout test framework for comparison.
+  void SendPng() {
+    // Send image header & hash_ to the layout test framework.
+    printf("Content-Type: image/png\n");
+    printf("ActualHash: %s\n", base::MD5DigestToBase16(hash_).data());
+    printf("Content-Length: %" PRIuS "\n", output_.size());
+
+    for (size_t i = 0; i < output_.size(); ++i)
+      printf("%c", output_[i]);
+
+    printf("#EOF\n");
+    fflush(stdout);
+    fprintf(stderr, "#EOF\n");
+    fflush(stderr);
+  }
+
+  // Duplicates the tab that was created when the browser opened.
+  // This is done, so that the observer can listen to the duplicated
+  // tab as soon as possible and start listening for messages related to
+  // print preview.
+  void DuplicateTab() {
+    WebContents* tab =
+        browser()->tab_strip_model()->GetActiveWebContents();
+    ASSERT_TRUE(tab);
+
+    print_preview_observer_.reset(
+        new PrintPreviewObserver(tab, browser()));
+    chrome::DuplicateTab(browser());
+
+    WebContents* initiator =
+        browser()->tab_strip_model()->GetActiveWebContents();
+    ASSERT_TRUE(initiator);
+    ASSERT_NE(tab, initiator);
+  }
+
+  // Resets the test so that another web page can be printing.
+  // Deletes the duplicate tab as it isn't needed anymore.
+  void Reset() {
+    output_.clear();
+    ASSERT_EQ(browser()->tab_strip_model()->count(), 2);
+    chrome::CloseTab(browser());
+    ASSERT_EQ(browser()->tab_strip_model()->count(), 1);
+  }
+
+  // Creates a temporary directory to store the file that will be used for
+  // stdin to accept input. Also sets up the path to save the pdf file
+  // that will be printed. Everything is cleaned up automatically once
+  // the test ends.
+  void SetupStdinAndSavePath() {
+    // Sends a message to the layout test framework indicating indicating
+    // that the browser test has completed setting itself up. The layout
+    // test will then expect the file path for stdin.
+    printf("#READY\n");
+    fflush(stdout);
+
+    ASSERT_TRUE(tmp_dir_.CreateUniqueTempDir());
+    ASSERT_TRUE(base::CreateTemporaryFileInDir(tmp_dir_.path(), &tmp_path_));
+    ASSERT_TRUE(freopen(tmp_path_.value().c_str(), "r", stdin));
+
+    pdf_file_save_path_ = tmp_dir_.path().AppendASCII("dummy.pdf");
+
+    // Send the file path to the layout test framework so that it can
+    // communicate with this browsertest.
+    printf("StdinPath: %s\n#EOF\n", tmp_path_.value().c_str());
+    fflush(stdout);
+  }
+
+ private:
+  scoped_ptr<PrintPreviewObserver> print_preview_observer_;
+  base::FilePath pdf_file_save_path_;
+
+  typedef bool (*PDFPageToBitmap)(const void* pdf_buffer,
+                                  int pdf_buffer_size,
+                                  int page_number,
+                                  void* bitmap_buffer,
+                                  int bitmap_width,
+                                  int bitmap_height,
+                                  int dpi_x,
+                                  int dpi_y,
+                                  bool autorotate);
+
+  typedef bool (*GetPDFDocInfoProc)(const void* pdf_buffer,
+                                    int buffer_size,
+                                    int* pages_count,
+                                    double* max_page_width);
+
+  typedef bool (*GetPDFPageSizeByIndexProc)(const void* pdf_buffer,
+                                            int buffer_size,
+                                            int index,
+                                            double* width,
+                                            double* height);
+
+  PDFPageToBitmap pdf_to_bitmap_func_;
+  GetPDFDocInfoProc pdf_doc_info_func_;
+  GetPDFPageSizeByIndexProc pdf_page_size_func_;
+  std::vector<unsigned char> output_;
+  base::MD5Digest hash_;
+  base::ScopedTempDir tmp_dir_;
+  base::FilePath tmp_path_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrintPreviewPdfGeneratedBrowserTest);
+};
+
+IN_PROC_BROWSER_TEST_F(PrintPreviewPdfGeneratedBrowserTest,
+                       MANUAL_DummyTest) {
+  // What this code is supposed to do:
+  // -Setup communication with the layout test framework
+  // -Print webpage to a pdf
+  // -Convert pdf to a png
+  // -Send png to layout test framework, where it doesn an image diff
+  //  on the image sent by this test and a reference image.
+  //
+  // Throughout this code, there will be printf statements.
+  // The layout test framework uses stdout to get data from the browser test
+  // and uses stdin to send data to the browser test.
+  // Calling printf("#EOF\n") indicates that whatever block of data that
+  // the test was expecting has been completely sent. Sometimes EOF is
+  // printed to stderr because the test will expect it from stderr
+  // in addition to stdout for certain blocks of data.
+  SetupStdinAndSavePath();
+
+  // There is no way to determine how many tests are to be run
+  // ahead of time without a ton of modifications to the layout
+  // test framework. However, whenever it is done with a set of tests,
+  // it calls SIGKILL on the browser test that ran those set of tests.
+  // Thus, this while loop will end once the layout test framework
+  // decides to actually kill this process. For this to work,
+  // the test must be run with '--single_process'. There must be an
+  // underscore, not a dash, as that is something different.
+  while (true) {
+    base::FilePath::StringType cmd;
+    std::getline(STDIN_STREAM, cmd);
+    if (cmd.empty()) {
+      while (STDIN_STREAM.eof()) {
+        STDIN_STREAM.clear();
+        std::getline(STDIN_STREAM, cmd);
+        if (!cmd.empty()) {
+          break;
+        }
+      }
+    }
+
+    DuplicateTab();
+
+    // TODO(ivandavid): Get settings from file in resources.
+    PrintPreviewSettings settings(
+        true,
+        "",
+        false,
+        false,
+        printing::DEFAULT_MARGINS,
+        cmd.find(".pdf") != base::FilePath::StringType::npos);
+
+    std::vector<base::FilePath::StringType> cmd_arguments;
+    base::SplitString(cmd, '\'', &cmd_arguments);
+    base::FilePath::StringType test_name(cmd_arguments[0]);
+    NavigateAndPreview(test_name, settings);
+    Print();
+    PdfToPng();
+
+    // Message to the layout test framework indicating that it should start
+    // waiting for the image data, as there is no more text data to be read.
+    // There actually isn't any text data at all, however because the layout
+    // test framework requires it, a message has to be sent to stop it from
+    // waiting for this message and start waiting for the image data.
+    printf("#EOF\n");
+    fflush(stdout);
+
+    SendPng();
+    Reset();
+  }
+}