Add LEVELDB_EXPORT macro to export public symbols.

gcc defaults to exporting all symbols, but other linkers do not. Adding
the LEVELDB_EXPORT macro allows a project to set LEVELDB_SHARED_LIBRARY
when building/linking with leveldb as a shared library.

This is to allow leveldb to be created as a shared library on all
platforms support by Chrome and enables a fix for
https://bugs.chromium.org/p/chromium/issues/detail?id=764810.

This also has the benefit of reducing the shared library size from
418863 to 380367 bytes (64-bit Linux).

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=171037148

1 files changed, 2 insertions, 1 deletions

diff --git a/include/leveldb/table_builder.h b/include/leveldb/table_builder.h
index 5fd1dc7..3c3acc7 100644
--- a/include/leveldb/table_builder.h
+++ b/include/leveldb/table_builder.h
@@ -14,6 +14,7 @@
 #define STORAGE_LEVELDB_INCLUDE_TABLE_BUILDER_H_
 
 #include <stdint.h>
+#include "leveldb/export.h"
 #include "leveldb/options.h"
 #include "leveldb/status.h"
 
@@ -23,7 +24,7 @@ class BlockBuilder;
 class BlockHandle;
 class WritableFile;
 
-class TableBuilder {
+class LEVELDB_EXPORT TableBuilder {
  public:
   // Create a builder that will store the contents of the table it is
   // building in *file.  Does not close the file.  It is up to the