Disk cache: fix broken UMA reports.

net/disk_cache/entry_impl.cc

 // Copyright (c) 2006-2008 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 "net/disk_cache/entry_impl.h"
 
 #include "base/histogram.h"
 #include "base/message_loop.h"
 #include "base/string_util.h"
 #include "net/base/io_buffer.h"
@@ skipping 521 matching lines @@
     if (!entry->rankings()->Store()) {
       entry->Release();
       return NULL;
     }
     return entry;
   }
 }
 
 bool EntryImpl::IsDirty(int32 current_id) {
   DCHECK(node_.HasData());
+  // We are checking if the entry is valid or not. If there is a pointer here,
+  // |dirty| has to be the id of the cache that is using the entry (the one
+  // that created the pointer), 0 is not a valid id.
   if (node_.Data()->pointer && !node_.Data()->dirty)
     return true;
 
   return node_.Data()->dirty && current_id != node_.Data()->dirty;
 }
 
 void EntryImpl::ClearDirtyFlag() {
   node_.Data()->dirty = 0;
 }
 
@@ skipping 304 matching lines @@
   Trace("%s 0x%p 0x%x 0x%x", msg, reinterpret_cast<void*>(this),
         entry_.address().value(), node_.address().value());
 
   Trace("  data: 0x%x 0x%x 0x%x", entry_.Data()->data_addr[0],
         entry_.Data()->data_addr[1], entry_.Data()->long_key);
 
   Trace("  doomed: %d 0x%p 0x%x", doomed_, pointer, dirty);
 }
 
 }  // namespace disk_cache