Add UMA historgam to measure response handling time of ResourceLoader

Add Net.ResourceLoader.ResponseStartToEnd family that measures the time
elapsed from ResponseStarted to ResponseComplete.

BUG=580928

Review URL: https://codereview.chromium.org/1627293002

Cr-Commit-Position: refs/heads/master@{#372271}

3 files changed, 49 insertions, 0 deletions

diff --git a/content/browser/loader/async_resource_handler.cc b/content/browser/loader/async_resource_handler.cc
index e6b1ddf..f7ff190 100644
--- a/content/browser/loader/async_resource_handler.cc
+++ b/content/browser/loader/async_resource_handler.cc
@@ -207,6 +207,8 @@ bool AsyncResourceHandler::OnResponseStarted(ResourceResponse* response,
   // request commits, avoiding the possibility of e.g. zooming the old content
   // or of having to layout the new content twice.
 
+  response_started_ticks_ = base::TimeTicks::Now();
+
   progress_timer_.Stop();
   const ResourceRequestInfoImpl* info = GetRequestInfo();
   if (!info->filter())
@@ -412,6 +414,8 @@ void AsyncResourceHandler::OnResponseCompleted(
       request()->GetTotalReceivedBytes();
   info->filter()->Send(
       new ResourceMsg_RequestComplete(GetRequestID(), request_complete_data));
+
+  RecordHistogram();
 }
 
 bool AsyncResourceHandler::EnsureResourceBufferIsInitialized() {
@@ -457,4 +461,28 @@ int AsyncResourceHandler::CalculateEncodedDataLengthToReport() {
   return encoded_data_length;
 }
 
+void AsyncResourceHandler::RecordHistogram() {
+  int64_t elapsed_time =
+      (base::TimeTicks::Now() - response_started_ticks_).InMicroseconds();
+  int64_t encoded_length = request()->GetTotalReceivedBytes();
+  if (encoded_length < 2 * 1024) {
+    // The resource was smaller than the smallest required buffer size.
+    UMA_HISTOGRAM_CUSTOM_COUNTS("Net.ResourceLoader.ResponseStartToEnd.LT_2kB",
+                                elapsed_time, 1, 100000, 100);
+  } else if (encoded_length < 32 * 1024) {
+    // The resource was smaller than single chunk.
+    UMA_HISTOGRAM_CUSTOM_COUNTS("Net.ResourceLoader.ResponseStartToEnd.LT_32kB",
+                                elapsed_time, 1, 100000, 100);
+  } else if (encoded_length < 512 * 1024) {
+    // The resource was smaller than single chunk.
+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Net.ResourceLoader.ResponseStartToEnd.LT_512kB",
+        elapsed_time, 1, 100000, 100);
+  } else {
+    UMA_HISTOGRAM_CUSTOM_COUNTS(
+        "Net.ResourceLoader.ResponseStartToEnd.Over_512kB",
+        elapsed_time, 1, 100000, 100);
+  }
+}
+
 }  // namespace content
diff --git a/content/browser/loader/async_resource_handler.h b/content/browser/loader/async_resource_handler.h
index ca06ed3..f46fef9 100644
--- a/content/browser/loader/async_resource_handler.h
+++ b/content/browser/loader/async_resource_handler.h
@@ -67,6 +67,7 @@ class AsyncResourceHandler : public ResourceHandler,
   void OnDefer();
   bool CheckForSufficientResource();
   int CalculateEncodedDataLengthToReport();
+  void RecordHistogram();
 
   scoped_refptr<ResourceBuffer> buffer_;
   ResourceDispatcherHostImpl* rdh_;
@@ -83,6 +84,8 @@ class AsyncResourceHandler : public ResourceHandler,
   bool sent_received_response_msg_;
   bool sent_first_data_msg_;
 
+  base::TimeTicks response_started_ticks_;
+
   uint64_t last_upload_position_;
   bool waiting_for_upload_progress_ack_;
   base::TimeTicks last_upload_ticks_;
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index a8f848e..bc68c7b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -26663,6 +26663,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Net.ResourceLoader.ResponseStartToEnd" units="microseconds">
+  <owner>tzik@chromium.org</owner>
+  <summary>
+    Time from the start to the end of receiving a response body. Recorded for
+    each resource load.
+  </summary>
+</histogram>
+
 <histogram name="Net.ResponseSizeByProcess.Browser" units="KB">
   <owner>ttuttle@chromium.org</owner>
   <summary>
@@ -86103,6 +86111,16 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Media.EME.RequestMediaKeySystemAccess"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="ResourceLoaderSizeSlice" separator=".">
+  <suffix name="LT_2kB" label="Sliced for resources smaller than 2kB."/>
+  <suffix name="LT_32kB"
+      label="Sliced for resources smaller than 32kB and larger than 2kB."/>
+  <suffix name="LT_512kB"
+      label="Sliced for resources smaller than 512kB and larger than 32kB."/>
+  <suffix name="Over_512kB" label="Sliced for resources larger than 512kB."/>
+  <affected-histogram name="Net.ResourceLoader.ResponseStartToEnd"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="ResourcePrefetchPredictorNetworkTypePrefetch"
     separator=".">
   <suffix name="NotPrefetched"