Add UMA for time over deadline in Find-in-Page Scoping

Bug: 868227
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I4dc042dbcf7e38b71a64d1caa2982110e2796fef
Reviewed-on: https://chromium-review.googlesource.com/1193602Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587239}

third_party/blink/renderer/core/editing/finder/text_finder.cc

@@ -61,6 +61,7 @@
 #include "third_party/blink/renderer/core/layout/layout_view.h"
 #include "third_party/blink/renderer/core/layout/text_autosizer.h"
 #include "third_party/blink/renderer/core/page/page.h"
+#include "third_party/blink/renderer/platform/histogram.h"
 #include "third_party/blink/renderer/platform/timer.h"
 #include "third_party/blink/renderer/platform/wtf/time.h"
 
@@ -431,6 +432,9 @@ void TextFinder::ScopeStringMatches(IdleDeadline* deadline,
     return;
   }
 
+  const TimeDelta time_available =
+      TimeDelta::FromMillisecondsD(deadline->timeRemaining());
+  const TimeTicks start_time = CurrentTimeTicks();
   PositionInFlatTree search_start = PositionInFlatTree::FirstPositionInNode(
       *OwnerFrame().GetFrame()->GetDocument());
   PositionInFlatTree search_end = PositionInFlatTree::LastPositionInNode(
@@ -528,6 +532,10 @@ void TextFinder::ScopeStringMatches(IdleDeadline* deadline,
     next_scoping_start = search_start;
   } while (deadline->timeRemaining() > 0);
 
+  const TimeDelta time_spent = CurrentTimeTicks() - start_time;
+  UMA_HISTOGRAM_TIMES("WebCore.FindInPage.ScopingTime",
+                      time_spent - time_available);
+
   if (next_scoping_start.IsNotNull()) {
     resume_scoping_from_range_ =
         Range::Create(*next_scoping_start.GetDocument(),

tools/metrics/histograms/histograms.xml

@@ -112988,6 +112988,14 @@ uploading your change for review.
   </summary>
 </histogram>
 
+<histogram name="WebCore.FindInPage.ScopingTime">
+  <owner>rakina@chromium.org</owner>
+  <summary>
+    Records how much time it takes for find-in-page scoping over the idle task
+    deadline.
+  </summary>
+</histogram>
+
 <histogram name="WebCore.Framebust" enum="FramebustPermissions">
   <owner>japhet@chromium.org</owner>
   <summary>