Avoid large inlined automatic methods in IndexedDB code.

content/browser/indexed_db/indexed_db_backing_store.h

Index: content/browser/indexed_db/indexed_db_backing_store.h
diff --git a/content/browser/indexed_db/indexed_db_backing_store.h b/content/browser/indexed_db/indexed_db_backing_store.h
index 7c16b4e95a24cc6affcb1fc687dab52961bde25e..d7e5dbc217c24db517ce7af8df78df7b27c6edc5 100644
--- a/content/browser/indexed_db/indexed_db_backing_store.h
+++ b/content/browser/indexed_db/indexed_db_backing_store.h
@@ -167,7 +167,7 @@ class CONTENT_EXPORT IndexedDBBackingStore
     typedef std::vector<std::pair<BlobEntryKey, std::string> >
         BlobEntryKeyValuePairVec;
 
-    class WriteDescriptor {
+    class CONTENT_EXPORT WriteDescriptor {
      public:
       WriteDescriptor(const GURL& url,
                       int64_t key,
@@ -177,6 +177,9 @@ class CONTENT_EXPORT IndexedDBBackingStore
                       int64_t key,
                       int64_t size,
                       base::Time last_modified);
+      WriteDescriptor(const WriteDescriptor& other);
+      ~WriteDescriptor();
+      WriteDescriptor& operator=(const WriteDescriptor& other);
 
       bool is_file() const { return is_file_; }
       const GURL& url() const {