[Extensions] Add metrics for API binding generation time

extensions/renderer/module_system.cc

Index: extensions/renderer/module_system.cc
diff --git a/extensions/renderer/module_system.cc b/extensions/renderer/module_system.cc
index dd13786f198f9267b084caa0b810259205ef1e0e..6bf090f9cf165b2ddb76076e6e85a12d0e480d2f 100644
--- a/extensions/renderer/module_system.cc
+++ b/extensions/renderer/module_system.cc
@@ -8,8 +8,10 @@
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "base/timer/elapsed_timer.h"
 #include "base/trace_event/trace_event.h"
 #include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_view.h"
@@ -379,6 +381,7 @@ void ModuleSystem::LazyFieldGetterInner(
     v8::Local<v8::String> property,
     const v8::PropertyCallbackInfo<v8::Value>& info,
     RequireFunction require_function) {
+  base::ElapsedTimer timer;
   CHECK(!info.Data().IsEmpty());
   CHECK(info.Data()->IsObject());
   v8::Isolate* isolate = info.GetIsolate();
@@ -460,6 +463,8 @@ void ModuleSystem::LazyFieldGetterInner(
     NOTREACHED();
   }
   info.GetReturnValue().Set(new_field);
+
+  UMA_HISTOGRAM_TIMES("Extensions.ApiBindingGenerationTime", timer.Elapsed());
 }
 
 void ModuleSystem::SetLazyField(v8::Local<v8::Object> object,