Fix UAF in SetVisible().

SetVisible() may be called during Destroy() which may be called
during SetVisible().

This fixes the latest in a family of bugs that happen after an
instance is freed by code triggered by JS code while it's executing
a method.

The CL has a lot of protection for many of these points where JS
may be executed and potentially destroy objects. The return types
of many methods that may execute JS have been changed to bool,
indicating whether the instance is still alive after the call.

Bug: chromium:770148
Change-Id: If5a9db4d8d6aac10f4dd6b645922bb96c116684d
Reviewed-on: https://pdfium-review.googlesource.com/15190
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/fpdfsdk/pwl/cpwl_combo_box.h b/fpdfsdk/pwl/cpwl_combo_box.h
index 20744df169..6db721369b 100644
--- a/fpdfsdk/pwl/cpwl_combo_box.h
+++ b/fpdfsdk/pwl/cpwl_combo_box.h
@@ -56,7 +56,7 @@ class CPWL_ComboBox : public CPWL_Wnd {
   void NotifyLButtonDown(CPWL_Wnd* child, const CFX_PointF& pos) override;
   void NotifyLButtonUp(CPWL_Wnd* child, const CFX_PointF& pos) override;
   void CreateChildWnd(const CreateParams& cp) override;
-  void RePosChildWnd() override;
+  bool RePosChildWnd() override;
   CFX_FloatRect GetFocusRect() const override;
   void SetFocus() override;
   void KillFocus() override;
@@ -85,7 +85,9 @@ class CPWL_ComboBox : public CPWL_Wnd {
   void CreateEdit(const CreateParams& cp);
   void CreateButton(const CreateParams& cp);
   void CreateListBox(const CreateParams& cp);
-  void SetPopup(bool bPopup);
+
+  // Returns |true| iff this instance is still allocated.
+  bool SetPopup(bool bPopup);
 
   UnownedPtr<CPWL_Edit> m_pEdit;
   UnownedPtr<CPWL_CBButton> m_pButton;