Enable the cups backend only when --enable-native-cups is specified.

CUPS printers will now be selectable in the print menus.

NOTE: This does not enable printing to said printers.

BUG=607668

TEST=Launch chrome with --enable-native-cups flag, open print preview,
change printers.  See that CUPS printers are listed as available
printers.

Review-Url: https://codereview.chromium.org/1934013002
Cr-Commit-Position: refs/heads/master@{#402654}

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

@@ -141,6 +141,7 @@
 #include "net/socket/ssl_server_socket.h"
 #include "net/url_request/url_request.h"
 #include "net/url_request/url_request_context_getter.h"
+#include "printing/backend/print_backend.h"
 #include "ui/base/ime/chromeos/ime_keyboard.h"
 #include "ui/base/ime/chromeos/input_method_manager.h"
 #include "ui/base/touch/touch_device.h"
@@ -505,6 +506,10 @@ void ChromeBrowserMainPartsChromeos::PreProfileInit() {
     WizardController::SetZeroDelays();
   }
 
+  // Enable/disable native CUPS integration
+  printing::PrintBackend::SetNativeCupsEnabled(
+      parsed_command_line().HasSwitch(::switches::kEnableNativeCups));
+
   power_prefs_.reset(new PowerPrefs(PowerPolicyController::Get()));
 
   // In Aura builds this will initialize ash::Shell.

printing/BUILD.gn

@@ -123,13 +123,6 @@ component("printing") {
     ]
   }
 
-  if (is_chromeos) {
-    sources += [
-      "printing_context_no_system_dialog.cc",
-      "printing_context_no_system_dialog.h",
-    ]
-  }
-
   if (use_cups) {
     configs += [ ":cups" ]
 
@@ -177,15 +170,18 @@ component("printing") {
       "backend/cups_helper.cc",
       "backend/cups_helper.h",
       "backend/print_backend_cups.cc",
+      "backend/print_backend_cups.h",
     ]
   }
 
   if (is_chromeos) {
-    # PRINT_BACKEND_AVAILABLE disables the default dummy implementation
-    # of the print backend and enables a custom implementation instead.
     defines += [ "PRINT_BACKEND_AVAILABLE" ]
 
-    sources += [ "backend/print_backend_chromeos.cc" ]
+    sources += [
+      "backend/print_backend_chromeos.cc",
+      "printing_context_no_system_dialog.cc",
+      "printing_context_no_system_dialog.h",
+    ]
   } else if (is_linux) {  # Non-ChromeOS Linux.
     sources += [
       "printing_context_linux.cc",

printing/backend/print_backend.cc

@@ -4,6 +4,10 @@
 
 #include "printing/backend/print_backend.h"
 
+namespace {
+bool g_native_cups_enabled = false;
+}  // namespace
+
 namespace printing {
 
 PrinterBasicInfo::PrinterBasicInfo()
@@ -40,4 +44,14 @@ PrinterCapsAndDefaults::~PrinterCapsAndDefaults() {}
 
 PrintBackend::~PrintBackend() {}
 
+// static
+bool PrintBackend::GetNativeCupsEnabled() {
+  return g_native_cups_enabled;
+}
+
+// static
+void PrintBackend::SetNativeCupsEnabled(bool enabled) {
+  g_native_cups_enabled = enabled;
+}
+
 }  // namespace printing

printing/backend/print_backend.h

@@ -123,6 +123,11 @@ class PRINTING_EXPORT PrintBackend
   static scoped_refptr<PrintBackend> CreateInstance(
       const base::DictionaryValue* print_backend_settings);
 
+  // Returns the value of the native cups flag
+  static bool GetNativeCupsEnabled();
+
+  static void SetNativeCupsEnabled(bool enabled);
+
  protected:
   friend class base::RefCountedThreadSafe<PrintBackend>;
   virtual ~PrintBackend();

printing/backend/print_backend_chromeos.cc

@@ -5,6 +5,13 @@
 #include "printing/backend/print_backend.h"
 
 #include "base/logging.h"
+#include "base/values.h"
+#include "printing/backend/print_backend_consts.h"
+#include "url/gurl.h"
+
+#if defined(USE_CUPS)
+#include "printing/backend/print_backend_cups.h"
+#endif  // defined(USE_CUPS)
 
 namespace printing {
 
@@ -72,8 +79,27 @@ bool PrintBackendChromeOS::IsValidPrinter(const std::string& printer_name) {
 
 scoped_refptr<PrintBackend> PrintBackend::CreateInstance(
     const base::DictionaryValue* print_backend_settings) {
+  if (GetNativeCupsEnabled()) {
+#if defined(USE_CUPS)
+    std::string print_server_url_str;
+    std::string cups_blocking;
+    int encryption = HTTP_ENCRYPT_NEVER;
+    if (print_backend_settings) {
+      print_backend_settings->GetString(kCUPSPrintServerURL,
+                                        &print_server_url_str);
+
+      print_backend_settings->GetString(kCUPSBlocking, &cups_blocking);
+
+      print_backend_settings->GetInteger(kCUPSEncryption, &encryption);
+    }
+    GURL print_server_url(print_server_url_str.c_str());
+    return new PrintBackendCUPS(print_server_url,
+                                static_cast<http_encryption_t>(encryption),
+                                cups_blocking == kValueTrue);
+#endif  // defined(USE_CUPS)
+  }
+
   return new PrintBackendChromeOS();
 }
 
 }  // namespace printing
-

printing/backend/print_backend_cups.cc

@@ -2,12 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "printing/backend/print_backend.h"
+#include "printing/backend/print_backend_cups.h"
 
 #include <dlfcn.h>
 #include <errno.h>
 #include <pthread.h>
 
+#include <string>
+
 #include "base/debug/leak_annotations.h"
 #include "base/files/file_util.h"
 #include "base/lazy_instance.h"
@@ -68,43 +70,6 @@ bool PrinterBasicInfoFromCUPS(const cups_dest_t& printer,
 
 }  // namespace
 
-class PrintBackendCUPS : public PrintBackend {
- public:
-  PrintBackendCUPS(const GURL& print_server_url,
-                   http_encryption_t encryption, bool blocking);
-
- private:
-  ~PrintBackendCUPS() override {}
-
-  // PrintBackend implementation.
-  bool EnumeratePrinters(PrinterList* printer_list) override;
-  std::string GetDefaultPrinterName() override;
-  bool GetPrinterBasicInfo(const std::string& printer_name,
-                           PrinterBasicInfo* printer_info) override;
-  bool GetPrinterSemanticCapsAndDefaults(
-      const std::string& printer_name,
-      PrinterSemanticCapsAndDefaults* printer_info) override;
-  bool GetPrinterCapsAndDefaults(const std::string& printer_name,
-                                 PrinterCapsAndDefaults* printer_info) override;
-  std::string GetPrinterDriverInfo(const std::string& printer_name) override;
-  bool IsValidPrinter(const std::string& printer_name) override;
-
-  // The following functions are wrappers around corresponding CUPS functions.
-  // <functions>2() are called when print server is specified, and plain version
-  // in another case. There is an issue specifying CUPS_HTTP_DEFAULT in the
-  // functions>2(), it does not work in CUPS prior to 1.4.
-  int GetDests(cups_dest_t** dests);
-  base::FilePath GetPPD(const char* name);
-
-  // Wrapper around cupsGetNamedDest(). Returned result should be freed with
-  // cupsFreeDests().
-  cups_dest_t* GetNamedDest(const std::string& printer_name);
-
-  GURL print_server_url_;
-  http_encryption_t cups_encryption_;
-  bool blocking_;
-};
-
 PrintBackendCUPS::PrintBackendCUPS(const GURL& print_server_url,
                                    http_encryption_t encryption,
                                    bool blocking)
@@ -230,6 +195,7 @@ bool PrintBackendCUPS::IsValidPrinter(const std::string& printer_name) {
   return true;
 }
 
+#if !defined(OS_CHROMEOS)
 scoped_refptr<PrintBackend> PrintBackend::CreateInstance(
     const base::DictionaryValue* print_backend_settings) {
   std::string print_server_url_str, cups_blocking;
@@ -248,6 +214,7 @@ scoped_refptr<PrintBackend> PrintBackend::CreateInstance(
                               static_cast<http_encryption_t>(encryption),
                               cups_blocking == kValueTrue);
 }
+#endif  // !defined(OS_CHROMEOS)
 
 int PrintBackendCUPS::GetDests(cups_dest_t** dests) {
   if (print_server_url_.is_empty()) {  // Use default (local) print server.

printing/backend/print_backend_cups.h

+// Copyright 2016 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 PRINTING_BACKEND_PRINT_BACKEND_CUPS_H_
+#define PRINTING_BACKEND_PRINT_BACKEND_CUPS_H_
+
+#include <string>
+
+#include "base/files/file_util.h"
+#include "printing/backend/cups_helper.h"
+#include "printing/backend/print_backend.h"
+#include "url/gurl.h"
+
+namespace printing {
+
+class PrintBackendCUPS : public PrintBackend {
+ public:
+  PrintBackendCUPS(const GURL& print_server_url,
+                   http_encryption_t encryption,
+                   bool blocking);
+
+ private:
+  ~PrintBackendCUPS() override {}
+
+  // PrintBackend implementation.
+  bool EnumeratePrinters(PrinterList* printer_list) override;
+  std::string GetDefaultPrinterName() override;
+  bool GetPrinterBasicInfo(const std::string& printer_name,
+                           PrinterBasicInfo* printer_info) override;
+  bool GetPrinterSemanticCapsAndDefaults(
+      const std::string& printer_name,
+      PrinterSemanticCapsAndDefaults* printer_info) override;
+  bool GetPrinterCapsAndDefaults(const std::string& printer_name,
+                                 PrinterCapsAndDefaults* printer_info) override;
+  std::string GetPrinterDriverInfo(const std::string& printer_name) override;
+  bool IsValidPrinter(const std::string& printer_name) override;
+
+  // The following functions are wrappers around corresponding CUPS functions.
+  // <functions>2() are called when print server is specified, and plain version
+  // in another case. There is an issue specifying CUPS_HTTP_DEFAULT in the
+  // functions>2(), it does not work in CUPS prior to 1.4.
+  int GetDests(cups_dest_t** dests);
+  base::FilePath GetPPD(const char* name);
+
+  // Wrapper around cupsGetNamedDest(). Returned result should be freed with
+  // cupsFreeDests().
+  cups_dest_t* GetNamedDest(const std::string& printer_name);
+
+  GURL print_server_url_;
+  http_encryption_t cups_encryption_;
+  bool blocking_;
+};
+
+}  // namespace printing
+
+#endif  // PRINTING_BACKEND_PRINT_BACKEND_CUPS_H_