add metric for delay between when autocorrect occurs and when it is reverted

BUG=1110772

Change-Id: I9c960eb923612a97b9e5b65ba45c7dc4ba26bddf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2554741Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Keith Lee <keithlee@chromium.org>
Commit-Queue: John Palmer <jopalmer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832583}

chrome/browser/chromeos/input_method/autocorrect_manager.cc

@@ -53,6 +53,7 @@ void AutocorrectManager::HandleAutocorrect(gfx::Range autocorrect_range,
   ClearUnderline();
 
   input_context->SetAutocorrectRange(autocorrect_range);
+  autocorrect_time_ = base::TimeTicks::Now();
 }
 
 bool AutocorrectManager::OnKeyEvent(
@@ -177,6 +178,8 @@ void AutocorrectManager::UndoAutocorrect() {
            surrounding_text.surrounding_text.substr(0, range.start())) +
        original_text_));
   LogAssistiveAutocorrectAction(AutocorrectActions::kReverted);
+  base::UmaHistogramMediumTimes("InputMethod.Assistive.Autocorrect.Delay",
+                                (base::TimeTicks::Now() - autocorrect_time_));
 }
 
 }  // namespace chromeos

chrome/browser/chromeos/input_method/autocorrect_manager.h

@@ -54,6 +54,7 @@ class AutocorrectManager {
   std::string original_text_;
   bool window_visible = false;
   bool button_highlighted = false;
+  base::TimeTicks autocorrect_time_;
 };
 
 }  // namespace chromeos

tools/metrics/histograms/histograms_xml/input/histograms.xml

@@ -55,7 +55,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="InputMethod.Assistive.Autocorrect.Delay" units="ms"
-    expires_after="2021-01-01">
+    expires_after="2021-06-01">
   <owner>jopalmer@google.com</owner>
   <owner>essential-inputs-team@google.com</owner>
   <summary>