tools: implement blob write

Implement blob write bytes.

Change-Id: Ie7c79db67ea58a82d39ac679a8e380934e93ca5a
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/blob_interface_mock.hpp b/test/blob_interface_mock.hpp
index eff241f..bf9fdbc 100644
--- a/test/blob_interface_mock.hpp
+++ b/test/blob_interface_mock.hpp
@@ -9,6 +9,8 @@
 {
   public:
     virtual ~BlobInterfaceMock() = default;
+    MOCK_METHOD3(writeBytes, void(std::uint16_t, std::uint32_t,
+                                  const std::vector<std::uint8_t>&));
     MOCK_METHOD0(getBlobList, std::vector<std::string>());
     MOCK_METHOD1(getStat, StatResponse(const std::string&));
     MOCK_METHOD2(openBlob,