Android: Don't evict thumbnails for last visible tab on stop

chrome/browser/android/thumbnail/scoped_ptr_expiring_cache.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_ANDROID_THUMBNAIL_SCOPED_PTR_EXPIRING_CACHE_H_
 #define CHROME_BROWSER_ANDROID_THUMBNAIL_SCOPED_PTR_EXPIRING_CACHE_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 20 matching lines @@
     EvictIfFull();
   }
 
   Value* Get(const Key& key) {
     iterator iter = map_.find(key);
     if (iter != map_.end())
       return iter->second;
     return NULL;
   }
 
-  void Remove(const Key& key) {
+  std::unique_ptr<Value> Remove(const Key& key) {
     iterator iter = map_.find(key);
+    std::unique_ptr<Value> value;
     if (iter != map_.end()) {
-      delete iter->second;
+      value.reset(iter->second);
       map_.erase(key);
     }
+    return std::move(value);
   }
 
   void Clear() {
     for (iterator iter = map_.begin(); iter != map_.end(); iter++) {
       delete iter->second;
     }
     map_.clear();
   }
 
   iterator begin() { return map_.begin(); }
@@ skipping 10 matching lines @@
     }
   }
 
   size_t max_cache_size_;
   LinkedHashMap map_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedPtrExpiringCache);
 };
 
 #endif  // CHROME_BROWSER_ANDROID_THUMBNAIL_SCOPED_PTR_EXPIRING_CACHE_H_