Remove Stability.RendererUnresponsiveBeforeTermination histogram.

The histogram has been expired. Cleanup the dead code.

BUG=1061971

Change-Id: I2bd0a6096b464261e0bf60c50dfea28b172002a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2587374Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836689}

chrome/browser/ui/views/hung_renderer_view.cc

@@ -416,12 +416,6 @@ void HungRendererDialogView::WindowClosing() {
 }
 
 void HungRendererDialogView::ForceCrashHungRenderer() {
-  auto* render_widget_host = hung_pages_table_model_->GetRenderWidgetHost();
-  bool currently_unresponsive =
-      render_widget_host && render_widget_host->IsCurrentlyUnresponsive();
-  UMA_HISTOGRAM_BOOLEAN("Stability.RendererUnresponsiveBeforeTermination",
-                        currently_unresponsive);
-
   content::RenderProcessHost* rph =
       hung_pages_table_model_->GetRenderWidgetHost()->GetProcess();
   if (rph) {

tools/metrics/histograms/histograms_xml/stability/histograms.xml

@@ -515,6 +515,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="Stability.RendererUnresponsiveBeforeTermination"
     enum="BooleanUnresponsive" expires_after="2020-04-26">
+  <obsolete>
+    Removed 12/2020.
+  </obsolete>
   <owner>dtapuska@chromium.org</owner>
   <summary>
     If the renderer is considered unresponsive from the browser's perspective