Add UMA metrics for the time it takes to read store from disk and apply update

components/safe_browsing_db/v4_store_unittest.cc

Index: components/safe_browsing_db/v4_store_unittest.cc
diff --git a/components/safe_browsing_db/v4_store_unittest.cc b/components/safe_browsing_db/v4_store_unittest.cc
index 922048022e0cd895f3b7ea19daf2d4778ce1b9ff..90c6525fa88ca316d0051a6fabf0e73147e51e6f 100644
--- a/components/safe_browsing_db/v4_store_unittest.cc
+++ b/components/safe_browsing_db/v4_store_unittest.cc
@@ -708,8 +708,9 @@ TEST_F(V4StoreTest, TestAdditionsWithRiceEncodingFailsWithInvalidInput) {
   addition->set_compression_type(RICE);
   addition->mutable_rice_hashes()->set_num_entries(-1);
   HashPrefixMap additions_map;
-  EXPECT_EQ(RICE_DECODING_FAILURE, V4Store::UpdateHashPrefixMapFromAdditions(
-                                       additions, &additions_map));
+  EXPECT_EQ(RICE_DECODING_FAILURE,
+            V4Store(task_runner_, store_path_)
+                .UpdateHashPrefixMapFromAdditions(additions, &additions_map));
 }
 #endif
 
@@ -728,8 +729,9 @@ TEST_F(V4StoreTest, TestAdditionsWithRiceEncodingSucceeds) {
   rice_hashes->set_encoded_data(
       "\xbf\xa8\x3f\xfb\xf\xf\x5e\x27\xe6\xc3\x1d\xc6\x38");
   HashPrefixMap additions_map;
-  EXPECT_EQ(APPLY_UPDATE_SUCCESS, V4Store::UpdateHashPrefixMapFromAdditions(
-                                      additions, &additions_map));
+  EXPECT_EQ(APPLY_UPDATE_SUCCESS,
+            V4Store(task_runner_, store_path_)
+                .UpdateHashPrefixMapFromAdditions(additions, &additions_map));
   EXPECT_EQ(1u, additions_map.size());
   EXPECT_EQ(std::string("\x5\0\0\0\fL\x93\xADV\x7F\xF6o\xCEo1\x81", 16),
             additions_map[4]);