Include suppressed dialogs in the FineTiming histogram

components/app_modal/javascript_dialog_manager.cc

Index: components/app_modal/javascript_dialog_manager.cc
diff --git a/components/app_modal/javascript_dialog_manager.cc b/components/app_modal/javascript_dialog_manager.cc
index 0fcfb9228d3768daecbcf05da283bb2c1b446c1a..3dc55163ec73ef2e14d4aa4a028568559e79a345 100644
--- a/components/app_modal/javascript_dialog_manager.cc
+++ b/components/app_modal/javascript_dialog_manager.cc
@@ -94,6 +94,21 @@ void JavaScriptDialogManager::RunJavaScriptDialog(
       &javascript_dialog_extra_data_[web_contents];
 
   if (extra_data->suppress_javascript_messages_) {
+    // If a page tries to open dialogs in a tight loop, the number of
+    // suppressions logged can grow out of control. Arbitrarily cap the number
+    // logged at 100. That many suppressed dialogs is enough to indicate the
+    // page is doing something very hinky.
+    if (extra_data->suppressed_dialog_count_ < 100) {
+      // Log a suppressed dialog as one that opens and then closes immediately.
+      UMA_HISTOGRAM_MEDIUM_TIMES(
+          "JSDialogs.FineTiming.TimeBetweenDialogCreatedAndSameDialogClosed",
+          base::TimeDelta());
+
+      // Only increment the count if it's not already at the limit, to prevent
+      // overflow.
+      extra_data->suppressed_dialog_count_++;
+    }
+
     *did_suppress_message = true;
     return;
   }