update_engine: replace std::vector<char> with chromeos::Blob

To make update engine consistent with the rest of platform2 code
replaced std::vector<char> as the container of binary data with
chromeos::Blob.

BUG=None
TEST=`FEATURES=test emerge-link update_engine`

Change-Id: I6385fd2257d15aa24bfa74ac35512c2a06c33012
Reviewed-on: https://chromium-review.googlesource.com/247793
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/filesystem_copier_action_unittest.cc b/filesystem_copier_action_unittest.cc
index 5973fb6..5b4c3ab 100644
--- a/filesystem_copier_action_unittest.cc
+++ b/filesystem_copier_action_unittest.cc
@@ -139,12 +139,12 @@
 
   // Make random data for a, zero filled data for b.
   const size_t kLoopFileSize = 10 * 1024 * 1024 + 512;
-  vector<char> a_loop_data(kLoopFileSize);
+  chromeos::Blob a_loop_data(kLoopFileSize);
   test_utils::FillWithData(&a_loop_data);
-  vector<char> b_loop_data(run_out_of_space ?
-                           (kLoopFileSize - 1) :
-                           kLoopFileSize,
-                           '\0');  // Fill with 0s
+  chromeos::Blob b_loop_data(run_out_of_space ?
+                             (kLoopFileSize - 1) :
+                             kLoopFileSize,
+                             0);  // Fill with 0s
 
   // Write data to disk
   if (!(test_utils::WriteFileVector(a_loop_file, a_loop_data) &&
@@ -254,7 +254,7 @@
   EXPECT_EQ(ErrorCode::kSuccess, delegate.code());
 
   // Make sure everything in the out_image is there
-  vector<char> a_out;
+  chromeos::Blob a_out;
   if (!utils::ReadFile(a_dev, &a_out)) {
     ADD_FAILURE();
     return false;
@@ -264,7 +264,7 @@
   EXPECT_TRUE(is_a_file_reading_eq);
   success = success && is_a_file_reading_eq;
   if (!verify_hash) {
-    vector<char> b_out;
+    chromeos::Blob b_out;
     if (!utils::ReadFile(b_dev, &b_out)) {
       ADD_FAILURE();
       return false;