A crasher would sometimes happen when opening a selet file dialog

(such as when loading an unpacled extension).
This is because we would reinterpret cast the user data of the HWND
to a WidgetWin, and in that case the Windows dialog has a user-data
that we did not set.
This CL checks that the HWND is at least a WindowImpl before attempting
to retrieve the WidgetWin, ensuring we won't mess with windows we did
not create directly.

BUG=44312
TEST=Open the extension page. Move the focus by pressing TAB to the
     "Load unpacked extension..." button. Press ENTER many times quickly
     so it opens/closes the "Select dir" dialog. It should not crash.

Review URL: http://codereview.chromium.org/2124009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@47672 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 13 insertions, 0 deletions

diff --git a/app/win/window_impl.cc b/app/win/window_impl.cc
index 9668f82..5488434 100644
--- a/app/win/window_impl.cc
+++ b/app/win/window_impl.cc
@@ -152,6 +152,16 @@ HICON WindowImpl::GetDefaultWindowIcon() const {
   return NULL;
 }
 
+// static
+bool WindowImpl::IsWindowImpl(HWND hwnd) {
+  wchar_t tmp[128];
+  if (!::GetClassName(hwnd, tmp, 128))
+    return false;
+
+  std::wstring class_name(tmp);
+  return class_name.find(kBaseClassName) == 0;
+}
+
 LRESULT WindowImpl::OnWndProc(UINT message, WPARAM w_param, LPARAM l_param) {
   LRESULT result = 0;
 
diff --git a/app/win/window_impl.h b/app/win/window_impl.h
index ad1fc87..67f3bf7 100644
--- a/app/win/window_impl.h
+++ b/app/win/window_impl.h
@@ -70,6 +70,9 @@ class WindowImpl : public MessageMapInterface {
   }
   UINT initial_class_style() const { return class_style_; }
 
+  // Returns true if the specified |hwnd| is a WindowImpl.
+  static bool IsWindowImpl(HWND hwnd);
+
  protected:
   // Handles the WndProc callback for this object.
   virtual LRESULT OnWndProc(UINT message, WPARAM w_param, LPARAM l_param);