Add SafeBrowsing.BrowserThrottle.* metrics

The Safe Browsing check blocks the URL loader when the URL loader
starts to process the response. We'd like to know how often that happens
and how long does the Safe Browsing check block the URL loader.

Metrics added in this CL:
SafeBrowsing.BrowserThrottle.IsCheckCompletedOnProcessResponse
SafeBrowsing.BrowserThrottle.TotalDelay

Bug: 1144265
Change-Id: I7a14548170458e04fe9452647b347a84780819b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2510742
Commit-Queue: Xinghui Lu <xinghuilu@chromium.org>
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Reviewed-by: Weilun Shi <sweilun@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#823448}

components/safe_browsing/content/browser/browser_url_loader_throttle.cc

@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/check_op.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/trace_event/trace_event.h"
 #include "components/safe_browsing/core/browser/safe_browsing_url_checker_impl.h"
 #include "components/safe_browsing/core/browser/url_checker_delegate.h"
@@ -251,7 +252,12 @@ void BrowserURLLoaderThrottle::WillProcessResponse(
     return;
   }
 
-  if (pending_checks_ == 0)
+  bool check_completed = (pending_checks_ == 0);
+  base::UmaHistogramBoolean(
+      "SafeBrowsing.BrowserThrottle.IsCheckCompletedOnProcessResponse",
+      check_completed);
+
+  if (check_completed)
     return;
 
   DCHECK(!deferred_);
@@ -289,6 +295,8 @@ void BrowserURLLoaderThrottle::OnCompleteCheck(bool slow_check,
     if (pending_checks_ == 0 && deferred_) {
       deferred_ = false;
       TRACE_EVENT_ASYNC_END0("safe_browsing", "Deferred", this);
+      base::UmaHistogramTimes("SafeBrowsing.BrowserThrottle.TotalDelay",
+                              total_delay_);
       delegate_->Resume();
     }
   } else {

tools/metrics/histograms/histograms_xml/safe_browsing/histograms.xml

@@ -80,6 +80,31 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram
+    name="SafeBrowsing.BrowserThrottle.IsCheckCompletedOnProcessResponse"
+    enum="BooleanCompleted" expires_after="2021-10-30">
+  <owner>xinghuilu@chromium.org</owner>
+  <owner>chrome-safebrowsing-alerts@google.com</owner>
+  <summary>
+    Logs whether the Safe Browsing check is completed when the URL loader starts
+    to process a response. If not, the URL loader will be deferred until the
+    Safe Browsing check is completed. Logs each time the URL loader dispatches
+    WillProcessResponse() and the Safe Browsing check doesn't block the URL.
+  </summary>
+</histogram>
+
+<histogram name="SafeBrowsing.BrowserThrottle.TotalDelay" units="ms"
+    expires_after="2021-10-30">
+  <owner>xinghuilu@chromium.org</owner>
+  <owner>chrome-safebrowsing-alerts@google.com</owner>
+  <summary>
+    Logs the latency between when the URL loader was deferred by Safe Browsing
+    check and when the check is completed. Logs each time the URL loader was
+    deferred by Safe Browsing check and the Safe Browsing check doesn't block
+    the URL.
+  </summary>
+</histogram>
+
 <histogram name="SafeBrowsing.CheckBrowseUrl.HasLocalMatch"
     enum="BooleanMatched" expires_after="2021-08-05">
   <owner>vakh@chromium.org</owner>