Make the PrintDlgEx() call in the UI thread.

chrome/browser/printing/printer_query.cc

Index: chrome/browser/printing/printer_query.cc
===================================================================
--- chrome/browser/printing/printer_query.cc	(revision 13415)
+++ chrome/browser/printing/printer_query.cc	(working copy)
@@ -4,21 +4,20 @@
 
 #include "chrome/browser/printing/printer_query.h"
 
+#include "base/compiler_specific.h"
 #include "base/message_loop.h"
 #include "chrome/browser/printing/print_job_worker.h"
 
-#ifdef _MSC_VER
-#pragma warning(disable:4355)  // 'this' : used in base member initializer list
-#endif
-
 namespace printing {
 
-PrinterQuery::PrinterQuery()
-    : ui_message_loop_(MessageLoop::current()),
-      worker_(new PrintJobWorker(this)),
+PrinterQuery::PrinterQuery(MessageLoop* ui_message_loop)
+    : ui_message_loop_(ui_message_loop),
+      message_loop_(MessageLoop::current()),
+      ALLOW_THIS_IN_INITIALIZER_LIST(worker_(new PrintJobWorker(this))),
       is_print_dialog_box_shown_(false),
       last_status_(PrintingContext::FAILED),
       cookie_(PrintSettings::NewCookie()) {
+  DCHECK(ui_message_loop_);
 }
 
 PrinterQuery::~PrinterQuery() {
@@ -31,7 +30,7 @@
     callback_->Cancel();
   }
   // It may get deleted in a different thread that the one that created it.
-  // That's fine so don't DCHECK_EQ(ui_message_loop_, MessageLoop::current());
+  // That's fine so don't DCHECK_EQ(message_loop_, MessageLoop::current());
 }
 
 void PrinterQuery::GetSettingsDone(const PrintSettings& new_settings,
@@ -65,28 +64,41 @@
                                HWND parent_window,
                                int expected_page_count,
                                CancelableTask* callback) {
-  DCHECK_EQ(ui_message_loop_, MessageLoop::current());
+  DCHECK_EQ(message_loop_, MessageLoop::current());
   DCHECK(!is_print_dialog_box_shown_);
   DCHECK(!callback_.get());
   DCHECK(worker_.get());
   if (!worker_.get())
     return;
-  // Lazy create the worker thread. There is one worker thread per print job.
-  if (!worker_->message_loop()) {
-    if (!worker_->Start()) {
-      if (callback) {
-        callback->Cancel();
-        delete callback;
+
+  MessageLoop* message_loop;
+  if (ask_user_for_settings == DEFAULTS) {
+    // Lazy create the worker thread. There is one worker thread per print job.
+    if (!worker_->message_loop()) {
+      if (!worker_->Start()) {
+        if (callback) {
+          callback->Cancel();
+          delete callback;
+        }
+        callback_.reset(NULL);
+        NOTREACHED();
+        return;
       }
-      NOTREACHED();
-      return;
     }
+    message_loop = worker_->message_loop();
+  } else if (ask_user_for_settings == ASK_USER) {
+    // No need for a worker thread in that case.
+    message_loop = ui_message_loop_;
+  } else {
+    callback_.reset(NULL);
+    NOTREACHED();
+    return;
   }
-
+  DCHECK(message_loop);
+  is_print_dialog_box_shown_ = ask_user_for_settings == ASK_USER;
   callback_.reset(callback);
   // Real work is done in PrintJobWorker::Init().
-  is_print_dialog_box_shown_ = ask_user_for_settings == ASK_USER;
-  worker_->message_loop()->PostTask(FROM_HERE, NewRunnableMethod(
+  message_loop->PostTask(FROM_HERE, NewRunnableMethod(
       worker_.get(),
       &PrintJobWorker::GetSettings,
       is_print_dialog_box_shown_,
@@ -113,4 +125,53 @@
   return worker_.get() != NULL;
 }
 
+
+DefaultSettingsPrinterQueryTask::DefaultSettingsPrinterQueryTask(
+    MessageLoop* reply_message_loop)
+    : reply_task_(new ReplyTask()),
+      reply_message_loop_(reply_message_loop) {
+  if (!reply_message_loop_)
+    reply_message_loop_ = MessageLoop::current();
+}
+
+void DefaultSettingsPrinterQueryTask::Run() {
+  DCHECK(reply_task_);
+  // Run the lengthy operation:
+  reply_task_->result_.Run();
+
+  // Post back the result.
+  reply_message_loop_->PostTask(FROM_HERE, reply_task_);
+  // |this| will be deleted upon return.
+}
+
+void DefaultSettingsPrinterQueryTask::Cancel() {
+  reply_task_->Cancel();
+  // |this| will be deleted upon return.
+}
+
+DefaultSettingsPrinterQueryTask::Result::Result()
+   : result(PrintingContext::FAILED) {
+}
+
+void DefaultSettingsPrinterQueryTask::Result::Run() {
+  result = printing_context.UseDefaultSettings();
+}
+
+DefaultSettingsPrinterQueryTask::ReplyTask::ReplyTask() {
+}
+
+void DefaultSettingsPrinterQueryTask::ReplyTask::Run() {
+  DCHECK(reply_task_.get());
+  reply_task_->Run();
+  reply_task_.reset(NULL);
+  // |this| will be deleted upon return.
+}
+
+void DefaultSettingsPrinterQueryTask::ReplyTask::Cancel() {
+  DCHECK(reply_task_.get());
+  reply_task_->Cancel();
+  reply_task_.reset(NULL);
+  // |this| will be deleted upon return.
+}
+
 }  // namespace printing