Cleanup: Remove unused variables in chrome/ found by Scythe.

chrome/browser/history/history_unittest.cc

Index: chrome/browser/history/history_unittest.cc
diff --git a/chrome/browser/history/history_unittest.cc b/chrome/browser/history/history_unittest.cc
index 9319e4879f7f6673070f4f1c523933d66c5ea793..b1a1275b9b70dc34547104ca9475151f200f15db 100644
--- a/chrome/browser/history/history_unittest.cc
+++ b/chrome/browser/history/history_unittest.cc
@@ -978,9 +978,7 @@ TEST_F(HistoryBackendDBTest,
 
 class HistoryTest : public testing::Test {
  public:
-  HistoryTest()
-      : got_thumbnail_callback_(false),
-        query_url_success_(false) {
+  HistoryTest() : query_url_success_(false) {
   }
 
   ~HistoryTest() override {}
@@ -1095,11 +1093,6 @@ class HistoryTest : public testing::Test {
   // names of the database files
   base::FilePath history_dir_;
 
-  // Set by the thumbnail callback when we get data, you should be sure to
-  // clear this before issuing a thumbnail request.
-  bool got_thumbnail_callback_;
-  std::vector<unsigned char> thumbnail_data_;
-
   // Set by the redirect callback when we get data. You should be sure to
   // clear this before issuing a redirect request.
   history::RedirectList saved_redirects_;