Blimp: add padding for zlib framing to buffer preallocation calculations.

blimp/net/compressed_packet_unittest.cc

Index: blimp/net/compressed_packet_unittest.cc
diff --git a/blimp/net/compressed_packet_unittest.cc b/blimp/net/compressed_packet_unittest.cc
index 61e39b88bb8779645626e61e92ee60387937f4bc..0742fda8d74659fb6abb0ee72bb9efe1d4fc54e0 100644
--- a/blimp/net/compressed_packet_unittest.cc
+++ b/blimp/net/compressed_packet_unittest.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/memory/ptr_util.h"
+#include "base/rand_util.h"
 #include "base/sys_byteorder.h"
 #include "blimp/net/common.h"
 #include "blimp/net/compressed_packet_reader.h"
@@ -153,6 +154,15 @@ TEST_F(CompressedPacketTest, LargeInput) {
   EXPECT_TRUE(CheckRoundTrip(big_str));
 }
 
+TEST_F(CompressedPacketTest, LowCompressionRatio) {
+  // This size (2338) was found "in the wild" to repro an issue with output
+  // buffer overflows.
+  const int data_size = 2338;
+
+  EXPECT_TRUE(CheckRoundTrip(base::RandBytesAsString(data_size)));
+  EXPECT_TRUE(CheckRoundTrip(base::RandBytesAsString(data_size)));
+}
+
 TEST_F(CompressedPacketTest, DecompressIllegallyLargePayload) {
   // We can't use the compressor to compress an illegally sized payload, however
   // we can concatenate the output of smaller payloads to form an uber-payload.