Squashed 'src/leveldb/' changes from 936b461..e991315

e991315 Merge upstream LevelDB 1.15.
0cfb990 Release LevelDB 1.15
02ac9f1 Merge upstream LevelDB 1.14.
0b9a89f Release LevelDB 1.14

git-subtree-dir: src/leveldb
git-subtree-split: e991315d7fe4ca84a98902578106cbffa3dcccfd

util/testutil.cc

@@ -32,7 +32,7 @@ std::string RandomKey(Random* rnd, int len) {
 
 
 extern Slice CompressibleString(Random* rnd, double compressed_fraction,
-                                int len, std::string* dst) {
+                                size_t len, std::string* dst) {
   int raw = static_cast<int>(len * compressed_fraction);
   if (raw < 1) raw = 1;
   std::string raw_data;