Add deadline to Find-in-page idle tasks

In some cases such as multiple frame webpages, idle task might never
execute or take a noticably long time to execute. This might lead to
incorrect number of find-in-page result and not highlighting matches
because the scoping is never trigerred. This CL adds a deadline to
scoping idle tasks to ensure all scoping happens in a timely manner.

Bug: 890622,893465
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: I8ec998d4c2f42377361c1f7b95c1497a80368ef6
Reviewed-on: https://chromium-review.googlesource.com/c/1270196
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599562}

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

@@ -67,6 +67,7 @@
 namespace blink {
 
 namespace {
+const int kScopingTimeoutMS = 100;
 constexpr TimeDelta kTextFinderTestTimeout = TimeDelta::FromSeconds(10);
 }
 
@@ -113,9 +114,15 @@ class TextFinder::IdleScopeStringMatchesCallback
         identifier_(identifier),
         search_text_(search_text),
         options_(options.Clone()) {
+    // We need to add deadline because some webpages might have frames
+    // that are always busy, resulting in bad experience in find-in-page
+    // because the scoping tasks are not run.
+    // See crbug.com/893465.
+    IdleRequestOptions request_options;
+    request_options.setTimeout(kScopingTimeoutMS);
     callback_handle_ =
         text_finder->GetFrame()->GetDocument()->RequestIdleCallback(
-            this, IdleRequestOptions());
+            this, request_options);
   }
 
   void invoke(IdleDeadline* deadline) override {