QUIC - Browser shutdown crash fix. Accessing disk_cache's backend after

it is deleted.

Did a one line fix to reset callback and commented out code that collected
UMA histogram data. Will implement correct fix asap.

TBR=rch@chromium.org
BUG=456524

Review URL: https://codereview.chromium.org/892083006

Cr-Commit-Position: refs/heads/master@{#315243}

net/http/disk_cache_based_quic_server_info.cc

@@ -104,7 +104,10 @@ int DiskCacheBasedQuicServerInfo::WaitForDataReady(
 void DiskCacheBasedQuicServerInfo::CancelWaitForDataReadyCallback() {
   DCHECK(CalledOnValidThread());
 
-  RecordQuicServerInfoStatus(QUIC_SERVER_INFO_WAIT_FOR_DATA_READY_CANCEL);
+  // TODO(rtenneti): crbug.com/456524. Implement a better fix. During shutdown,
+  // HttpCache could be deleted and leads to crash because backend_ is deleted.
+  // Temporary weekend fix is to return without collecting data in histograms.
+  // RecordQuicServerInfoStatus(QUIC_SERVER_INFO_WAIT_FOR_DATA_READY_CANCEL);
   if (!wait_for_ready_callback_.is_null()) {
     RecordLastFailure();
     wait_for_ready_callback_.Reset();

net/http/disk_cache_based_quic_server_info_unittest.cc

@@ -418,6 +418,28 @@ TEST(DiskCacheBasedQuicServerInfo, CancelWaitForDataReadyButDataIsReady) {
   RemoveMockTransaction(&kHostInfoTransaction1);
 }
 
+TEST(DiskCacheBasedQuicServerInfo, CancelWaitForDataReadyAfterDeleteCache) {
+  scoped_ptr<QuicServerInfo> quic_server_info;
+  {
+    MockHttpCache cache;
+    AddMockTransaction(&kHostInfoTransaction1);
+    TestCompletionCallback callback;
+
+    QuicServerId server_id("www.google.com", 443, true, PRIVACY_MODE_DISABLED);
+    quic_server_info.reset(
+        new DiskCacheBasedQuicServerInfo(server_id, cache.http_cache()));
+    EXPECT_FALSE(quic_server_info->IsDataReady());
+    quic_server_info->Start();
+    int rv = quic_server_info->WaitForDataReady(callback.callback());
+    quic_server_info->CancelWaitForDataReadyCallback();
+    EXPECT_EQ(OK, callback.GetResult(rv));
+    EXPECT_TRUE(quic_server_info->IsDataReady());
+    RemoveMockTransaction(&kHostInfoTransaction1);
+  }
+  // Cancel the callback after Cache is deleted.
+  quic_server_info->CancelWaitForDataReadyCallback();
+}
+
 // Test Start() followed by Persist() without calling WaitForDataReady.
 TEST(DiskCacheBasedQuicServerInfo, StartAndPersist) {
   MockHttpCache cache;