Prepare /storage/browser/database for TestCompletionCallback with non-repeating callbacks

Make sure that we don't re-use the callbacks from TestCompletionCallback,
so that we're prepared for when they become non-repeating callbacks (i.e.
base::CompletionOnceCallback), instead of base::CompletionCallback.

This CL was uploaded by git cl split.

TBR=pwnall@chromium.org

Bug: 807724
Change-Id: I430cf751ded3734a7ff7895e890da66b840ca823
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1541191
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Reviewed-by: Bence Béky <bnc@chromium.org>
Auto-Submit: Mario Sanchez Prada <mario@igalia.com>
Cr-Commit-Position: refs/heads/master@{#645228}

storage/browser/database/database_tracker_unittest.cc

@@ -232,15 +232,15 @@ class DatabaseTracker_TestHelper_Test {
     // Delete db1. Should also delete origin1.
     TestObserver observer;
     tracker->AddObserver(&observer);
-    net::TestCompletionCallback callback;
-    int result = tracker->DeleteDatabase(kOrigin1, kDB1, callback.callback());
+    net::TestCompletionCallback callback1;
+    int result = tracker->DeleteDatabase(kOrigin1, kDB1, callback1.callback());
     EXPECT_EQ(net::ERR_IO_PENDING, result);
-    ASSERT_FALSE(callback.have_result());
+    ASSERT_FALSE(callback1.have_result());
     EXPECT_TRUE(observer.DidReceiveNewNotification());
     EXPECT_EQ(kOrigin1, observer.GetNotificationOriginIdentifier());
     EXPECT_EQ(kDB1, observer.GetNotificationDatabaseName());
     tracker->DatabaseClosed(kOrigin1, kDB1);
-    result = callback.GetResult(result);
+    result = callback1.GetResult(result);
     EXPECT_EQ(net::OK, result);
     EXPECT_FALSE(base::PathExists(tracker->GetOriginDirectory(kOrigin1)));
 
@@ -265,13 +265,15 @@ class DatabaseTracker_TestHelper_Test {
     // Delete databases modified since yesterday. db2 is whitelisted.
     base::Time yesterday = base::Time::Now();
     yesterday -= base::TimeDelta::FromDays(1);
-    result = tracker->DeleteDataModifiedSince(yesterday, callback.callback());
+
+    net::TestCompletionCallback callback2;
+    result = tracker->DeleteDataModifiedSince(yesterday, callback2.callback());
     EXPECT_EQ(net::ERR_IO_PENDING, result);
-    ASSERT_FALSE(callback.have_result());
+    ASSERT_FALSE(callback2.have_result());
     EXPECT_TRUE(observer.DidReceiveNewNotification());
     tracker->DatabaseClosed(kOrigin1, kDB1);
     tracker->DatabaseClosed(kOrigin2, kDB2);
-    result = callback.GetResult(result);
+    result = callback2.GetResult(result);
     EXPECT_EQ(net::OK, result);
     EXPECT_FALSE(base::PathExists(tracker->GetOriginDirectory(kOrigin1)));
     EXPECT_TRUE(base::PathExists(tracker->GetFullDBFilePath(kOrigin2, kDB2)));