fix leak of hbitmap

skia/ext/raster_handle_allocator_win.cc

Index: skia/ext/raster_handle_allocator_win.cc
diff --git a/skia/ext/raster_handle_allocator_win.cc b/skia/ext/raster_handle_allocator_win.cc
index 93e1a252159d01b11b9bafc31041737b20676a0e..013cd50aa0e48846a302aece98266d4fcef41264 100644
--- a/skia/ext/raster_handle_allocator_win.cc
+++ b/skia/ext/raster_handle_allocator_win.cc
@@ -21,9 +21,20 @@ namespace {
 
 static void DeleteHDCCallback(void*, void* context) {
   HDC hdc = static_cast<HDC>(context);
-  HBITMAP hbitmap = static_cast<HBITMAP>(SelectObject(hdc, nullptr));
-  DeleteObject(hbitmap);
-  DeleteDC(hdc);
+
+  // We must get this before we call RestoreDC, as that will drop hbitmap and
+  // reselect the original/default bitmap.
+  HBITMAP hbitmap = static_cast<HBITMAP>(GetCurrentObject(hdc, OBJ_BITMAP));
+  DCHECK(hbitmap);

[f(malita), 2017/01/13 15:51:57]

nit: DCHECK_NE(hbitmap, nullptr)

[reed1, 2017/01/13 15:58:08]

Done.

+
+  int success = RestoreDC(hdc, -1); // effectly performs the deselect of hbitmap

[f(malita), 2017/01/13 15:51:57]

nit: bool

[reed1, 2017/01/13 15:58:08]

Done.

+  DCHECK(success);
+
+  // Now we are the only owner, so we can delete our bitmap
+  success = DeleteObject(hbitmap);
+  DCHECK(hbitmap);

[f(malita), 2017/01/13 15:51:57]

DCHECK_NE

[reed1, 2017/01/13 15:58:08]

Done.

+  success = DeleteDC(hdc);
+  DCHECK(hbitmap);

[f(malita), 2017/01/13 15:51:57]

DCHECK_NE

[reed1, 2017/01/13 15:58:08]

Done.

 }
 
 // Allocate the layer and fill in the fields for the Rec, or return false
@@ -52,6 +63,11 @@ static bool Create(int width,
     return false;
   }
   SetGraphicsMode(hdc, GM_ADVANCED);
+
+  int saveIndex = SaveDC(hdc);  // so we can Restore in the delete callback
+  DCHECK(saveIndex != 0);

[f(malita), 2017/01/13 15:52:44]

DCHECK_NE(saveIndex, 0)

[reed1, 2017/01/13 15:58:08]

Done.

+
+  // Be sure to select *after* we called SaveDC.
   SelectObject(hdc, hbitmap);
 
   rec->fReleaseProc = DeleteHDCCallback;