[subresource_filter] Add metrics for all NavigationThrottle delays

components/subresource_filter/content/browser/activation_state_computing_navigation_throttle.cc

Index: components/subresource_filter/content/browser/activation_state_computing_navigation_throttle.cc
diff --git a/components/subresource_filter/content/browser/activation_state_computing_navigation_throttle.cc b/components/subresource_filter/content/browser/activation_state_computing_navigation_throttle.cc
index 0e755245c872288e89c058fef4010c9bb05cf36e..c48f137f6c72bee341f713b8d5dd072d487aebef 100644
--- a/components/subresource_filter/content/browser/activation_state_computing_navigation_throttle.cc
+++ b/components/subresource_filter/content/browser/activation_state_computing_navigation_throttle.cc
@@ -9,6 +9,7 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "components/subresource_filter/content/browser/async_document_subresource_filter.h"
 #include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/render_frame_host.h"
@@ -92,6 +93,8 @@ ActivationStateComputingNavigationThrottle::WillProcessResponse() {
       base::Bind(&ActivationStateComputingNavigationThrottle::
                      OnActivationStateComputed,
                  weak_ptr_factory_.GetWeakPtr()));
+
+  defer_timestamp_ = base::TimeTicks::Now();
   return content::NavigationThrottle::ThrottleCheckResult::DEFER;
 }
 
@@ -101,6 +104,15 @@ const char* ActivationStateComputingNavigationThrottle::GetNameForLogging() {
 
 void ActivationStateComputingNavigationThrottle::OnActivationStateComputed(
     ActivationState state) {
+  DCHECK(!defer_timestamp_.is_null());
+  base::TimeDelta delay = base::TimeTicks::Now() - defer_timestamp_;
+  UMA_HISTOGRAM_TIMES("SubresourceFilter.DocumentLoad.ActivationComputingDelay",

[pkalinnikov, 2017/05/08 12:00:05]

Do you expect it to be mostly >= 1 ms?

We also have microseconds-precision macros in
c/s_f/core/common/time_measurements.h (see UMA_HISTOGRAM_MICRO_TIMES).

[Charlie Harrison, 2017/05/08 12:53:33]

Yeah we can us microseconds for these metrics (maybe for the filtering ones as
well). I think I would feel more comfortable in the latter case using a
histogram with a ceiling > 1 second though using custom times.

+                      delay);
+  if (navigation_handle()->IsInMainFrame()) {
+    UMA_HISTOGRAM_TIMES(
+        "SubresourceFilter.DocumentLoad.ActivationComputingDelay.MainFrame",
+        delay);
+  }
   navigation_handle()->Resume();
 }