Merge: Block nested system print dialogs on Windows.

Browser needs to allow nested tasks to update backgroud tabs.
If rendered requests new system dialog, asan build crashes in COMDLG32.dll

NOTRY=true
BUG=451753

Review URL: https://codereview.chromium.org/934393003

Cr-Commit-Position: refs/heads/master@{#317611}
(cherry picked from commit a58ec6a)

Conflicts:
    printing/printing_context_win.cc

R=alekseys@chromium.org

Review URL: https://codereview.chromium.org/947223003

Cr-Commit-Position: refs/branch-heads/2272@{#365}
Cr-Branched-From: 827a380-refs/heads/master@{#310958}

Committed: https://chromium.googlesource.com/chromium/src/+/4c02af6cec7529da8acf1cffdbd468afe0cbc36e

Review URL: https://codereview.chromium.org/947223003

Cr-Commit-Position: refs/branch-heads/2272@{#367}
Cr-Branched-From: 827a380-refs/heads/master@{#310958}

printing/printing_context_system_dialog_win.cc

@@ -4,6 +4,7 @@
 
 #include "printing/printing_context_system_dialog_win.h"
 
+#include "base/auto_reset.h"
 #include "base/message_loop/message_loop.h"
 #include "printing/backend/win_helper.h"
 #include "printing/print_settings_initializer_win.h"
@@ -84,6 +85,13 @@ void PrintingContextSytemDialogWin::Cancel() {
 }
 
 HRESULT PrintingContextSytemDialogWin::ShowPrintDialog(PRINTDLGEX* options) {
+  // Runs always on the UI thread.
+  static bool is_dialog_shown = false;
+  if (is_dialog_shown)
+    return E_FAIL;
+  // Block opening dialog from nested task. It crashes PrintDlgEx.
+  base::AutoReset<bool> auto_reset(&is_dialog_shown, true);
+
   // Note that this cannot use ui::BaseShellDialog as the print dialog is
   // system modal: opening it from a background thread can cause Windows to
   // get the wrong Z-order which will make the print dialog appear behind the

printing/printing_context_win.cc

@@ -363,7 +363,7 @@ PrintingContext::Result PrintingContextWin::InitializeSettings(
 HWND PrintingContextWin::GetRootWindow(gfx::NativeView view) {
   HWND window = NULL;
 #if defined(USE_AURA)
-  if (view)
+  if (view && view->GetHost())
     window = view->GetHost()->GetAcceleratedWidget();
 #else
   if (view && IsWindow(view)) {