fix GDI usage errors in font precache

content/common/font_cache_dispatcher_win.cc

 // Copyright (c) 2011 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 "content/common/font_cache_dispatcher_win.h"
 
 #include <vector>
 #include <map>
 
 #include "base/logging.h"
@@ skipping 38 matching lines @@
     if (it == dispatcher_font_map_[dispatcher].end()) {
       // Requested font is new to cache.
       dispatcher_font_map_[dispatcher].push_back(font_name);
     } else {
       ref_count_inc = 0;
     }
 
     if (cache_[font_name].ref_count_ == 0) {  // Requested font is new to cache.
       cache_[font_name].ref_count_ = 1;
     } else {  // Requested font is already in cache, release old handles.
+      SelectObject(cache_[font_name].dc_, cache_[font_name].old_font_);
       DeleteObject(cache_[font_name].font_);
-      DeleteDC(cache_[font_name].dc_);
+      ReleaseDC(NULL, cache_[font_name].dc_);
     }
     cache_[font_name].font_ = font_handle;
     cache_[font_name].dc_ = hdc;
+    cache_[font_name].old_font_ = old_font;
     cache_[font_name].ref_count_ += ref_count_inc;
   }
 
   void ReleaseCachedFonts(FontCacheDispatcher* dispatcher) {
     typedef std::map<string16, FontCache::CacheElement> FontNameToElement;
 
     base::AutoLock lock(mutex_);
 
     DispatcherToFontNames::iterator it;
     it = dispatcher_font_map_.find(dispatcher);
@@ skipping 16 matching lines @@
         cache_.erase(i++);
       } else {
         ++i;
       }
     }
   }
 
  private:
   struct CacheElement {
     CacheElement()
-        : font_(NULL), dc_(NULL), ref_count_(0) {
+        : font_(NULL), old_font_(NULL), dc_(NULL), ref_count_(0) {
     }
 
     ~CacheElement() {
       if (font_) {
+        if (dc_ && old_font_) {
+          SelectObject(dc_, old_font_);
+        }
         DeleteObject(font_);
       }
       if (dc_) {
-        DeleteDC(dc_);
+        ReleaseDC(NULL, dc_);
       }
     }
 
     HFONT font_;
+    HGDIOBJ old_font_;
     HDC dc_;
     int ref_count_;
   };
   friend struct DefaultSingletonTraits<FontCache>;
 
   FontCache() {
   }
 
   std::map<string16, CacheElement> cache_;
   DispatcherToFontNames dispatcher_font_map_;
@@ skipping 53 matching lines @@
   // when a font is asked to be cached, we always recreates the font object
   // to avoid the case that an in-cache font is swapped out by GDI.
   FontCache::GetInstance()->PreCacheFont(font, this);
 }
 
 void FontCacheDispatcher::OnReleaseCachedFonts() {
   // Release cached fonts that requested from a pid by decrementing the ref
   // count.  When ref count is zero, the handles are released.
   FontCache::GetInstance()->ReleaseCachedFonts(this);
 }