FontAccess: Enumeration timer for windows

Adds an UMA metric to time font enumeration time on Windows.

Bug: 1043306
Change-Id: I6e8a3e51ee752f3e62388a08fd05b06456e7ccd3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2392992Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Stephen Chenney <schenney@chromium.org>
Auto-Submit: Olivier Yiptong <oyiptong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804493}

content/browser/font_access/font_enumeration_cache_win.cc

@@ -12,6 +12,7 @@
 #include "base/task/task_traits.h"
 #include "base/task/thread_pool.h"
 #include "base/threading/scoped_blocking_call.h"
+#include "base/timer/elapsed_timer.h"
 #include "third_party/blink/public/common/features.h"
 #include "ui/gfx/win/direct_write.h"
 
@@ -261,6 +262,9 @@ void FontEnumerationCacheWin::SchedulePrepareFontEnumerationCache() {
 
 void FontEnumerationCacheWin::PrepareFontEnumerationCache() {
   DCHECK(!enumeration_cache_built_.IsSet());
+  DCHECK(!enumeration_timer_);
+
+  enumeration_timer_ = std::make_unique<base::ElapsedTimer>();
 
   font_enumeration_table_ = std::make_unique<blink::FontEnumerationTable>();
 
@@ -317,6 +321,7 @@ void FontEnumerationCacheWin::AppendFontDataAndFinalizeIfNeeded(
 
 void FontEnumerationCacheWin::FinalizeEnumerationCache() {
   DCHECK(!enumeration_cache_built_.IsSet());
+  DCHECK(enumeration_timer_);
 
   if (enumeration_errors_.size() > 0) {
     auto most_frequent_hresult = std::max_element(
@@ -347,6 +352,10 @@ void FontEnumerationCacheWin::FinalizeEnumerationCache() {
 
   enumeration_cache_built_.Set();
 
+  UMA_HISTOGRAM_MEDIUM_TIMES("Fonts.AccessAPI.EnumerationTime",
+                             enumeration_timer_->Elapsed());
+  enumeration_timer_.reset();
+
   // Respond to pending and future requests.
   StartCallbacksTaskQueue();
 }

content/browser/font_access/font_enumeration_cache_win.h

@@ -21,6 +21,8 @@ using blink::mojom::FontEnumerationStatus;
 namespace base {
 template <typename T>
 class NoDestructor;
+
+class ElapsedTimer;
 }
 
 namespace content {
@@ -68,6 +70,7 @@ class CONTENT_EXPORT FontEnumerationCacheWin : public FontEnumerationCache {
   uint32_t outstanding_family_results_ = 0;
 
   std::map<HRESULT, unsigned> enumeration_errors_;
+  std::unique_ptr<base::ElapsedTimer> enumeration_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(FontEnumerationCacheWin);
 };