Add superficial unit test for PrintJob. That's a start....

chrome/browser/printing/print_job.cc

 // Copyright (c) 2006-2008 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/print_job.h"
 
 #include "base/message_loop.h"
 #include "chrome/browser/printing/print_job_worker.h"
 #include "chrome/browser/printing/printed_document.h"
 #include "chrome/browser/printing/printed_page.h"
 
 #ifdef _MSC_VER
 #pragma warning(disable:4355)  // 'this' : used in base member initializer list
 #endif
 
 using base::TimeDelta;
 
 namespace printing {
 
 PrintJob::PrintJob(PrintedPagesSource* source)
     : ui_message_loop_(MessageLoop::current()),
       worker_(new PrintJobWorker(this)),
       source_(source),
       is_job_pending_(false),
       is_print_dialog_box_shown_(false),
       is_canceling_(false) {
+  DCHECK(ui_message_loop_);
+  ui_message_loop_->AddDestructionObserver(this);
 }
 
 PrintJob::PrintJob()
     : ui_message_loop_(MessageLoop::current()),
       worker_(),
       source_(NULL),
       settings_(),
       is_job_pending_(false),
       is_print_dialog_box_shown_(false),
       is_canceling_(false) {
+  DCHECK(ui_message_loop_);
+  ui_message_loop_->AddDestructionObserver(this);
 }
 
 PrintJob::~PrintJob() {
+  ui_message_loop_->RemoveDestructionObserver(this);
   // The job should be finished (or at least canceled) when it is destroyed.
   DCHECK(!is_job_pending_);
   DCHECK(!is_print_dialog_box_shown_);
   DCHECK(!is_canceling_);
-  DCHECK(worker_->message_loop() == NULL);
+  if (worker_.get())
+    DCHECK(worker_->message_loop() == NULL);
   DCHECK_EQ(ui_message_loop_, MessageLoop::current());
 }
 
 void PrintJob::Initialize(PrintJobWorkerOwner* job,
                           PrintedPagesSource* source) {
   DCHECK(!source_);
   DCHECK(!worker_.get());
   DCHECK(!is_job_pending_);
   DCHECK(!is_print_dialog_box_shown_);
   DCHECK(!is_canceling_);
@@ skipping 80 matching lines @@
   return NULL;
 }
 
 int PrintJob::cookie() const {
   if (!document_.get())
     // Always use an invalid cookie in this case.
     return 0;
   return document_->cookie();
 }
 
+void PrintJob::WillDestroyCurrentMessageLoop() {
+  NOTREACHED();
+}
+
 void PrintJob::GetSettings(GetSettingsAskParam ask_user_for_settings,
                            HWND parent_window) {
   DCHECK_EQ(ui_message_loop_, MessageLoop::current());
   DCHECK(!is_job_pending_);
   DCHECK(!is_print_dialog_box_shown_);
   // Is not reentrant.
   if (is_job_pending_)
     return;
 
   // Lazy create the worker thread. There is one worker thread per print job.
@@ skipping 293 matching lines @@
 PrintedDocument* JobEventDetails::document() const {
   return document_;
 }
 
 PrintedPage* JobEventDetails::page() const {
   return page_;
 }
 
 }  // namespace printing