[Extensions] Add metrics for UserScriptListener

chrome/browser/extensions/user_script_listener.cc

Index: chrome/browser/extensions/user_script_listener.cc
diff --git a/chrome/browser/extensions/user_script_listener.cc b/chrome/browser/extensions/user_script_listener.cc
index 232b365e0067ea526dc364614f3f2da6bab14da0..dd7060a1b626265f72aca1a7342b75645e8924e0 100644
--- a/chrome/browser/extensions/user_script_listener.cc
+++ b/chrome/browser/extensions/user_script_listener.cc
@@ -5,6 +5,8 @@
 #include "chrome/browser/extensions/user_script_listener.h"
 
 #include "base/bind.h"
+#include "base/metrics/histogram.h"

[Mark P, 2015/03/19 18:59:15]

histogram_macros is more appropriate

[Devlin, 2015/03/19 19:45:54]

Done.

+#include "base/timer/elapsed_timer.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/extensions/manifest_handlers/content_scripts_handler.h"
@@ -34,8 +36,11 @@ class UserScriptListener::Throttle
     DCHECK(should_defer_);
     should_defer_ = false;
     // Only resume the request if |this| has deferred it.
-    if (did_defer_)
+    if (did_defer_) {
+      UMA_HISTOGRAM_TIMES("Extensions.ThrottledNetworkRequestDelay",
+                          timer_->Elapsed());

[not at google - send to devlin, 2015/03/19 15:41:14]

For completeness, timer_.reset()?

[Devlin, 2015/03/19 16:59:52]

These are deleted right after resume is called, but on the offchance the API
somehow changes and multiple resumes are allowed, it almost seems like then this
would still do the right thing. ;)

       controller()->Resume();
+    }
   }
 
   // ResourceThrottle implementation:
@@ -44,6 +49,7 @@ class UserScriptListener::Throttle
     if (should_defer_) {
       *defer = true;
       did_defer_ = true;
+      timer_.reset(new base::ElapsedTimer());
     }
   }
 
@@ -54,6 +60,9 @@ class UserScriptListener::Throttle
  private:
   bool should_defer_;
   bool did_defer_;
+  scoped_ptr<base::ElapsedTimer> timer_;
+
+  DISALLOW_COPY_AND_ASSIGN(Throttle);
 };
 
 struct UserScriptListener::ProfileData {
@@ -131,6 +140,8 @@ bool UserScriptListener::ShouldDelayRequest(const GURL& url,
 }
 
 void UserScriptListener::StartDelayedRequests() {
+  UMA_HISTOGRAM_COUNTS_100("Extensions.ThrottledNetworkRequests",
+                           throttles_.size());
   WeakThrottleList::const_iterator it;
   for (it = throttles_.begin(); it != throttles_.end(); ++it) {
     if (it->get())