Add HttpCache histograms focussed on blocking and transaction type.

net/http/http_cache_transaction.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/http/http_cache_transaction.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <unistd.h>
@@ skipping 21 matching lines @@
 #include "net/http/http_request_info.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_transaction.h"
 #include "net/http/http_util.h"
 #include "net/http/partial_data.h"
 
 using base::Time;
 using base::TimeDelta;
 using base::TimeTicks;
 
+namespace {
+
+// The cutoff for tagging small transactions in histograms; this size was chosen
+// to cover resources likely to be received in a single TCP window. With an
+// initial CWND of 10, and an MTU of 1500 bytes, with TCP and HTTP framing
+// overhead this is a size relatively likely to take only one RTT.
+const int kSmallResourceMaxBytes = 14 * 1024;
+
+}  // namespace
+
 namespace net {
 
 struct HeaderNameAndValue {
   const char* name;
   const char* value;
 };
 
 // If the request includes one of these request headers, then avoid caching
 // to avoid getting confused.
 static const HeaderNameAndValue kPassThroughHeaders[] = {
@@ skipping 67 matching lines @@
       handling_206_(false),
       cache_pending_(false),
       done_reading_(false),
       read_offset_(0),
       effective_load_flags_(0),
       write_len_(0),
       final_upload_progress_(0),
       ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)),
       ALLOW_THIS_IN_INITIALIZER_LIST(io_callback_(
           base::Bind(&Transaction::OnIOComplete,
-                     weak_factory_.GetWeakPtr()))) {
+                     weak_factory_.GetWeakPtr()))),
+      transaction_pattern_(PATTERN_UNDEFINED),
+      bytes_read_from_cache_(0),
+      bytes_read_from_network_(0) {
   COMPILE_ASSERT(HttpCache::Transaction::kNumValidationHeaders ==
                  arraysize(kValidationHeaders),
                  Invalid_number_of_validation_headers);
 }
 
 HttpCache::Transaction::~Transaction() {
   // We may have to issue another IO, but we should never invoke the callback_
   // after this point.
   callback_.Reset();
 
@@ skipping 523 matching lines @@
                                     result);
   cache_pending_ = false;
 
   if (!ShouldPassThrough()) {
     cache_key_ = cache_->GenerateCacheKey(request_);
 
     // Requested cache access mode.
     if (effective_load_flags_ & LOAD_ONLY_FROM_CACHE) {
       mode_ = READ;
     } else if (effective_load_flags_ & LOAD_BYPASS_CACHE) {
+      UpdateTransactionPattern(PATTERN_NOT_COVERED);
       mode_ = WRITE;
     } else {
       mode_ = READ_WRITE;
     }
 
     // Downgrade to UPDATE if the request has been externally conditionalized.
     if (external_validation_.initialized) {
       if (mode_ & WRITE) {
         // Strip off the READ_DATA bit (and maybe add back a READ_META bit
         // in case READ was off).
@@ skipping 28 matching lines @@
   // This is only set if we have something to do with the response.
   range_requested_ = (partial_.get() != NULL);
 
   return OK;
 }
 
 int HttpCache::Transaction::DoSendRequest() {
   DCHECK(mode_ & WRITE || mode_ == NONE);
   DCHECK(!network_trans_.get());
 
+  send_request_since_ = TimeTicks::Now();
+
   // Create a network transaction.
   int rv = cache_->network_layer_->CreateTransaction(&network_trans_);
   if (rv != OK)
     return rv;
 
   next_state_ = STATE_SEND_REQUEST_COMPLETE;
   rv = network_trans_->Start(request_, io_callback_, net_log_);
   return rv;
 }
 
 int HttpCache::Transaction::DoSendRequestComplete(int result) {
   if (!cache_)
     return ERR_UNEXPECTED;
 
   if (result == OK) {
     next_state_ = STATE_SUCCESSFUL_SEND_REQUEST;
     return OK;
   }
 
+  // Do not record requests that have network errors or restarts.
+  UpdateTransactionPattern(PATTERN_NOT_COVERED);
   if (IsCertificateError(result)) {
     const HttpResponseInfo* response = network_trans_->GetResponseInfo();
     // If we get a certificate error, then there is a certificate in ssl_info,
     // so GetResponseInfo() should never return NULL here.
     DCHECK(response);
     response_.ssl_info = response->ssl_info;
   } else if (result == ERR_SSL_CLIENT_AUTH_CERT_NEEDED) {
     const HttpResponseInfo* response = network_trans_->GetResponseInfo();
     DCHECK(response);
     response_.cert_request_info = response->cert_request_info;
@@ skipping 10 matching lines @@
     auth_response_ = *new_response;
     return OK;
   }
 
   new_response_ = new_response;
   if (!ValidatePartialResponse() && !auth_response_.headers) {
     // Something went wrong with this request and we have to restart it.
     // If we have an authentication response, we are exposed to weird things
     // hapenning if the user cancels the authentication before we receive
     // the new response.
+    UpdateTransactionPattern(PATTERN_NOT_COVERED);
     response_ = HttpResponseInfo();
     network_trans_.reset();
     new_response_ = NULL;
     next_state_ = STATE_SEND_REQUEST;
     return OK;
   }
+  bytes_read_from_network_ += new_response_->headers->raw_headers().size();
   if (handling_206_ && mode_ == READ_WRITE && !truncated_ && !is_sparse_) {
     // We have stored the full entry, but it changed and the server is
     // sending a range. We have to delete the old entry.
     DoneWritingToEntry(false);
   }
-
   if (new_response_->headers->response_code() == 416) {
     DCHECK_EQ(NONE, mode_);
     response_ = *new_response_;
     return OK;
   }
 
   if (mode_ == WRITE &&
       (request_->method == "PUT" || request_->method == "DELETE")) {
     if (new_response->headers->response_code() == 200) {
       int ret = cache_->DoomEntry(cache_key_, NULL);
       DCHECK_EQ(OK, ret);
     }
     mode_ = NONE;
   }
 
   // Are we expecting a response to a conditional query?
   if (mode_ == READ_WRITE || mode_ == UPDATE) {
     if (new_response->headers->response_code() == 304 || handling_206_) {
+      UpdateTransactionPattern(PATTERN_ENTRY_VALIDATED);
       next_state_ = STATE_UPDATE_CACHED_RESPONSE;
       return OK;
     }
+    UpdateTransactionPattern(PATTERN_ENTRY_UPDATED);
     mode_ = WRITE;
   }
 
   next_state_ = STATE_OVERWRITE_CACHED_RESPONSE;
   return OK;
 }
 
 int HttpCache::Transaction::DoNetworkRead() {
   next_state_ = STATE_NETWORK_READ_COMPLETE;
   return network_trans_->Read(read_buf_, io_buf_len_, io_callback_);
 }
 
 int HttpCache::Transaction::DoNetworkReadComplete(int result) {
   DCHECK(mode_ & WRITE || mode_ == NONE);
 
   if (!cache_)
     return ERR_UNEXPECTED;
 
+  if (result > 0)
+    bytes_read_from_network_ += result;
+
   // If there is an error or we aren't saving the data, we are done; just wait
   // until the destructor runs to see if we can keep the data.
   if (mode_ == NONE || result < 0)
     return result;
 
   next_state_ = STATE_CACHE_WRITE_DATA;
   return result;
 }
 
 int HttpCache::Transaction::DoInitEntry() {
   DCHECK(!new_entry_);
 
   if (!cache_)
     return ERR_UNEXPECTED;
 
   if (mode_ == WRITE) {
     next_state_ = STATE_DOOM_ENTRY;
     return OK;
   }
 
   next_state_ = STATE_OPEN_ENTRY;
   return OK;
 }
 
 int HttpCache::Transaction::DoOpenEntry() {
   DCHECK(!new_entry_);
   next_state_ = STATE_OPEN_ENTRY_COMPLETE;
   cache_pending_ = true;
   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_OPEN_ENTRY);
+  open_entry_since_ = TimeTicks::Now();
   return cache_->OpenEntry(cache_key_, &new_entry_, this);
 }
 
 int HttpCache::Transaction::DoOpenEntryComplete(int result) {
   // It is important that we go to STATE_ADD_TO_ENTRY whenever the result is
   // OK, otherwise the cache will end up with an active entry without any
   // transaction attached.
   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_OPEN_ENTRY, result);
   cache_pending_ = false;
   if (result == OK) {
     next_state_ = STATE_ADD_TO_ENTRY;
     return OK;
   }
 
   if (result == ERR_CACHE_RACE) {
     next_state_ = STATE_INIT_ENTRY;
     return OK;
   }
 
+  UpdateTransactionPattern(PATTERN_ENTRY_NOT_CACHED);
   if (request_->method == "PUT" || request_->method == "DELETE") {
     DCHECK(mode_ == READ_WRITE || mode_ == WRITE);
     mode_ = NONE;
     next_state_ = STATE_SEND_REQUEST;
     return OK;
   }
 
   if (mode_ == READ_WRITE) {
     mode_ = WRITE;
     next_state_ = STATE_CREATE_ENTRY;
@@ skipping 332 matching lines @@
                                       io_buf_len_, io_callback_);
 }
 
 int HttpCache::Transaction::DoCacheReadResponseComplete(int result) {
   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_INFO, result);
   if (result != io_buf_len_ ||
       !HttpCache::ParseResponseInfo(read_buf_->data(), io_buf_len_,
                                     &response_, &truncated_)) {
     return OnCacheReadError(result, true);
   }
+  bytes_read_from_cache_ += result;
 
   // Some resources may have slipped in as truncated when they're not.
   int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
   if (response_.headers->GetContentLength() == current_size)
     truncated_ = false;
 
   // We now have access to the cache entry.
   //
   //  o if we are a reader for the transaction, then we can start reading the
   //    cache entry.
   //
   //  o if we can read or write, then we should check if the cache entry needs
   //    to be validated and then issue a network request if needed or just read
   //    from the cache if the cache entry is already valid.
   //
   //  o if we are set to UPDATE, then we are handling an externally
   //    conditionalized request (if-modified-since / if-none-match). We check
   //    if the request headers define a validation request.
   //
   switch (mode_) {
     case READ:
+      UpdateTransactionPattern(PATTERN_ENTRY_USED);
       result = BeginCacheRead();
       break;
     case READ_WRITE:
       result = BeginPartialCacheValidation();
       break;
     case UPDATE:
       result = BeginExternallyConditionalizedRequest();
       break;
     case WRITE:
     default:
@@ skipping 44 matching lines @@
   net_log_.BeginEvent(NetLog::TYPE_HTTP_CACHE_READ_INFO);
   return entry_->disk_entry->ReadData(kMetadataIndex, 0, response_.metadata,
                                       response_.metadata->size(),
                                       io_callback_);
 }
 
 int HttpCache::Transaction::DoCacheReadMetadataComplete(int result) {
   net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_INFO, result);
   if (result != response_.metadata->size())
     return OnCacheReadError(result, false);
-
   return OK;
 }
 
 int HttpCache::Transaction::DoCacheQueryData() {
   next_state_ = STATE_CACHE_QUERY_DATA_COMPLETE;
 
   // Balanced in DoCacheQueryDataComplete.
   return entry_->disk_entry->ReadyForSparseIO(io_callback_);
 }
 
@@ skipping 22 matching lines @@
 
 int HttpCache::Transaction::DoCacheReadDataComplete(int result) {
   if (net_log_.IsLoggingAllEvents()) {
     net_log_.EndEventWithNetErrorCode(NetLog::TYPE_HTTP_CACHE_READ_DATA,
                                       result);
   }
 
   if (!cache_)
     return ERR_UNEXPECTED;
 
-  if (partial_.get())
+  if (partial_.get()) {
+    // Partial requests are confusing to report in histograms because they may
+    // have multiple underlying requests.
+    UpdateTransactionPattern(PATTERN_NOT_COVERED);
     return DoPartialCacheReadCompleted(result);
+  }
 
   if (result > 0) {
     read_offset_ += result;
+    bytes_read_from_cache_ += result;
   } else if (result == 0) {  // End of file.
+    RecordHistograms();
     cache_->DoneReadingFromEntry(entry_, this);
     entry_ = NULL;
   } else {
     return OnCacheReadError(result, false);
   }
   return result;
 }
 
 int HttpCache::Transaction::DoCacheWriteData(int num_bytes) {
   next_state_ = STATE_CACHE_WRITE_DATA_COMPLETE;
@@ skipping 127 matching lines @@
 
   // If there is more than one validation header, we can't treat this request as
   // a cache validation, since we don't know for sure which header the server
   // will give us a response for (and they could be contradictory).
   if (external_validation_error) {
     LOG(WARNING) << "Multiple or malformed validation headers found.";
     effective_load_flags_ |= LOAD_DISABLE_CACHE;
   }
 
   if (range_found && !(effective_load_flags_ & LOAD_DISABLE_CACHE)) {
+    UpdateTransactionPattern(PATTERN_NOT_COVERED);
     partial_.reset(new PartialData);
     if (request_->method == "GET" && partial_->Init(request_->extra_headers)) {
       // We will be modifying the actual range requested to the server, so
       // let's remove the header here.
       custom_request_.reset(new HttpRequestInfo(*request_));
       custom_request_->extra_headers.RemoveHeader(HttpRequestHeaders::kRange);
       request_ = custom_request_.get();
       partial_->SetHeaders(custom_request_->extra_headers);
     } else {
       // The range is invalid or we cannot handle it properly.
@@ skipping 51 matching lines @@
 
   return OK;
 }
 
 int HttpCache::Transaction::BeginCacheValidation() {
   DCHECK(mode_ == READ_WRITE);
 
   bool skip_validation = effective_load_flags_ & LOAD_PREFERRING_CACHE ||
                          !RequiresValidation();
 
-  if (truncated_)
+  if (truncated_) {
+    // Truncated entries can cause partial gets, so we shouldn't record this
+    // load in histograms.
+    UpdateTransactionPattern(PATTERN_NOT_COVERED);
     skip_validation = !partial_->initial_validation();
+  }
 
   if ((partial_.get() && !partial_->IsCurrentRangeCached()) || invalid_range_)
     skip_validation = false;
 
   if (skip_validation) {
+    UpdateTransactionPattern(PATTERN_ENTRY_USED);
     if (partial_.get()) {
       // We are going to return the saved response headers to the caller, so
       // we may need to adjust them first.
       next_state_ = STATE_PARTIAL_HEADERS_RECEIVED;
       return OK;
     }
     cache_->ConvertWriterToReader(entry_);
     mode_ = READ;
 
     if (entry_->disk_entry->GetDataSize(kMetadataIndex))
       next_state_ = STATE_CACHE_READ_METADATA;
   } else {
     // Make the network request conditional, to see if we may reuse our cached
     // response.  If we cannot do so, then we just resort to a normal fetch.
     // Our mode remains READ_WRITE for a conditional request.  We'll switch to
     // either READ or WRITE mode once we hear back from the server.
     if (!ConditionalizeRequest()) {
+      UpdateTransactionPattern(PATTERN_NOT_COVERED);
       DCHECK(!partial_.get());
       DCHECK_NE(206, response_.headers->response_code());
       mode_ = WRITE;
     }
     next_state_ = STATE_SEND_REQUEST;
   }
   return OK;
 }
 
 int HttpCache::Transaction::BeginPartialCacheValidation() {
   DCHECK(mode_ == READ_WRITE);
 
   if (response_.headers->response_code() != 206 && !partial_.get() &&
       !truncated_)
     return BeginCacheValidation();
 
+  // Partial requests should not be recorded in histograms.
+  UpdateTransactionPattern(PATTERN_NOT_COVERED);
   if (range_requested_) {
     next_state_ = STATE_CACHE_QUERY_DATA;
     return OK;
   }
   // The request is not for a range, but we have stored just ranges.
   partial_.reset(new PartialData());
   partial_->SetHeaders(request_->extra_headers);
   if (!custom_request_.get()) {
     custom_request_.reset(new HttpRequestInfo(*request_));
     request_ = custom_request_.get();
@@ skipping 40 matching lines @@
     std::string validator;
     response_.headers->EnumerateHeader(
         NULL,
         kValidationHeaders[i].related_response_header_name,
         &validator);
 
     if (response_.headers->response_code() != 200 || truncated_ ||
         validator.empty() || validator != external_validation_.values[i]) {
       // The externally conditionalized request is not a validation request
       // for our existing cache entry. Proceed with caching disabled.
+      UpdateTransactionPattern(PATTERN_NOT_COVERED);
       DoneWritingToEntry(true);
     }
   }
 
   next_state_ = STATE_SEND_REQUEST;
   return OK;
 }
 
 int HttpCache::Transaction::RestartNetworkRequest() {
   DCHECK(mode_ & WRITE || mode_ == NONE);
@@ skipping 203 matching lines @@
     }
 
     // 304 is not expected here, but we'll spare the entry (unless it was
     // truncated).
     if (truncated_)
       failure = true;
   }
 
   if (failure) {
     // We cannot truncate this entry, it has to be deleted.
+    UpdateTransactionPattern(PATTERN_NOT_COVERED);
     DoomPartialEntry(false);
     mode_ = NONE;
     if (!reading_ && !partial_->IsLastRange()) {
       // We'll attempt to issue another network request, this time without us
       // messing up the headers.
       partial_->RestoreHeaders(&custom_request_->extra_headers);
       partial_.reset();
       truncated_ = false;
       return false;
     }
@@ skipping 102 matching lines @@
 
   int current_size = entry_->disk_entry->GetDataSize(kResponseContentIndex);
   return WriteToEntry(kResponseContentIndex, current_size, data, data_len,
                       callback);
 }
 
 void HttpCache::Transaction::DoneWritingToEntry(bool success) {
   if (!entry_)
     return;
 
-  if (cache_->mode() == RECORD)
-    DVLOG(1) << "Recorded: " << request_->method << request_->url
-             << " status: " << response_.headers->response_code();
+  RecordHistograms();
 
   cache_->DoneWritingToEntry(entry_, success);
   entry_ = NULL;
   mode_ = NONE;  // switch to 'pass through' mode
 }
 
 int HttpCache::Transaction::OnCacheReadError(int result, bool restart) {
   DLOG(ERROR) << "ReadData failed: " << result;
 
   // Avoid using this entry in the future.
@@ skipping 74 matching lines @@
       !response_.headers->HasStrongValidators())
     return false;
 
   return true;
 }
 
 void HttpCache::Transaction::OnIOComplete(int result) {
   DoLoop(result);
 }
 
+void HttpCache::Transaction::UpdateTransactionPattern(
+    TransactionPattern new_transaction_pattern) {
+  if (transaction_pattern_ == PATTERN_NOT_COVERED)
+    return;
+  DCHECK(transaction_pattern_ == PATTERN_UNDEFINED ||
+         new_transaction_pattern == PATTERN_NOT_COVERED);
+  transaction_pattern_ = new_transaction_pattern;
+}
+
+void HttpCache::Transaction::RecordHistograms() {
+  DCHECK_NE(PATTERN_UNDEFINED, transaction_pattern_);
+  if (!cache_ || !cache_->GetCurrentBackend() ||
+      cache_->GetCurrentBackend()->GetCacheType() != DISK_CACHE ||
+      cache_->mode() != NORMAL || request_->method != "GET") {
+    return;
+  }
+  UMA_HISTOGRAM_BOOLEAN("HttpCache.HasPattern",
+                        transaction_pattern_ != PATTERN_NOT_COVERED);
+  if (transaction_pattern_ == PATTERN_NOT_COVERED)
+    return;
+  DCHECK(!range_requested_);
+  DCHECK(!open_entry_since_.is_null());
+
+  TimeDelta total_time = base::TimeTicks::Now() - open_entry_since_;
+
+  UMA_HISTOGRAM_TIMES("HttpCache.OpenToEnd", total_time);
+
+  bool did_send_request = !send_request_since_.is_null();
+  DCHECK(
+      (did_send_request && (transaction_pattern_ == PATTERN_ENTRY_NOT_CACHED ||
+                            transaction_pattern_ == PATTERN_ENTRY_VALIDATED ||
+                            transaction_pattern_ == PATTERN_ENTRY_UPDATED)) ||
+      (!did_send_request && transaction_pattern_ == PATTERN_ENTRY_USED));
+
+  int resource_size = -1;
+  if (transaction_pattern_ == PATTERN_ENTRY_NOT_CACHED ||
+      transaction_pattern_ == PATTERN_ENTRY_UPDATED) {
+      resource_size = bytes_read_from_network_;
+  } else if (transaction_pattern_ == PATTERN_ENTRY_VALIDATED ||

[rvargas (doing something else), 2012/07/30 21:09:31]

nit: simple else and DCHECK the pattern.

[gavinp, 2012/07/31 15:58:48]

Done.

+             transaction_pattern_ == PATTERN_ENTRY_USED) {
+      resource_size = bytes_read_from_cache_;
+  } else {
+      NOTREACHED();
+  }
+  bool is_small_resource = resource_size < kSmallResourceMaxBytes;
+  if (is_small_resource)
+    UMA_HISTOGRAM_TIMES("HttpCache.OpenToEnd.SmallResource", total_time);
+
+  if (!did_send_request) {
+    DCHECK(transaction_pattern_ == PATTERN_ENTRY_USED);
+    UMA_HISTOGRAM_TIMES("HttpCache.OpenToEnd.Used", total_time);
+    if (is_small_resource)
+      UMA_HISTOGRAM_TIMES("HttpCache.OpenToEnd.Used.SmallResource", total_time);
+    return;
+  }
+
+  TimeDelta before_send_time = send_request_since_ - open_entry_since_;
+  if (is_small_resource) {
+    UMA_HISTOGRAM_TIMES("HttpCache.SentRequest.OpenToEnd.SmallResource",
+                        total_time);
+    UMA_HISTOGRAM_TIMES("HttpCache.SentRequest.BeforeSend.SmallResource",
+                        before_send_time);
+  }
+
+  int before_send_percent = before_send_time * 100 / total_time;
+  DCHECK_LE(0, before_send_percent);
+  DCHECK_GE(100, before_send_percent);
+
+  UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend", before_send_percent);
+  UMA_HISTOGRAM_TIMES("HttpCache.SentRequest.OpenToEnd", total_time);
+  UMA_HISTOGRAM_TIMES("HttpCache.SentRequest.BeforeSend", before_send_time);
+  if (is_small_resource) {
+    UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.SmallResource",
+                             before_send_percent);
+  }
+
+  // TODO(gavinp): Remove or minimize these histograms, particularly the ones
+  // below this comment after we have received initial data.
+  switch (transaction_pattern_) {
+    case PATTERN_ENTRY_NOT_CACHED: {
+      UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.NotCached", before_send_time);
+      UMA_HISTOGRAM_PERCENTAGE(
+          "HttpCache.PercentBeforeSend.NotCached", before_send_percent);
+      if (is_small_resource) {
+        UMA_HISTOGRAM_PERCENTAGE(
+            "HttpCache.PercentBeforeSend.NotCached.SmallResource",
+            before_send_percent);
+      }
+      break;
+    }
+    case PATTERN_ENTRY_VALIDATED: {
+      UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.Validated", before_send_time);
+      UMA_HISTOGRAM_PERCENTAGE(
+          "HttpCache.PercentBeforeSend.Validated", before_send_percent);
+      if (is_small_resource) {
+        UMA_HISTOGRAM_PERCENTAGE(
+            "HttpCache.PercentBeforeSend.Validated.SmallResource",
+            before_send_percent);
+      }
+      break;
+    }
+    case PATTERN_ENTRY_UPDATED: {
+      UMA_HISTOGRAM_TIMES("HttpCache.TimeBlocked.Updated", before_send_time);
+      UMA_HISTOGRAM_PERCENTAGE(
+          "HttpCache.PercentBeforeSend.Updated", before_send_percent);
+      if (is_small_resource) {
+        UMA_HISTOGRAM_PERCENTAGE(
+            "HttpCache.PercentBeforeSend.Updated.SmallResource",
+            before_send_percent);
+      }
+      break;
+    }
+    default:
+      NOTREACHED();
+  }
+}
+
 }  // namespace net