Add GetStoreSize() to ImageStore to know the actual db size.

components/enhanced_bookmarks/persistent_image_store.cc

Index: components/enhanced_bookmarks/persistent_image_store.cc
diff --git a/components/enhanced_bookmarks/persistent_image_store.cc b/components/enhanced_bookmarks/persistent_image_store.cc
index 5e42f3528aa8e3358d36b25b099999397b8b4fc3..0108c85fc6549013e878284c10b4f4925af4e04c 100644
--- a/components/enhanced_bookmarks/persistent_image_store.cc
+++ b/components/enhanced_bookmarks/persistent_image_store.cc
@@ -4,6 +4,7 @@
 
 #include "components/enhanced_bookmarks/persistent_image_store.h"
 
+#include "base/files/file.h"
 #include "components/enhanced_bookmarks/image_store_util.h"
 #include "sql/statement.h"
 #include "sql/transaction.h"
@@ -197,6 +198,11 @@ void PersistentImageStore::ClearAll() {
   statement.Run();
 }
 
+int64 PersistentImageStore::GetStoreSizeInBytes() {
+  base::File file(path_, base::File::FLAG_OPEN | base::File::FLAG_READ);
+  return file.IsValid() ? file.GetLength() : -1;
+}
+
 PersistentImageStore::~PersistentImageStore() {
   DCHECK(sequence_checker_.CalledOnValidSequencedThread());
 }