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 f654f8bf3d01283202768bf81aebd77d655ae908..7c4db07af63ab2e967dcdb9e2dbb2dd659e6a4d5 100644
--- a/components/app_modal/javascript_dialog_manager.cc
+++ b/components/app_modal/javascript_dialog_manager.cc
@@ -104,6 +104,21 @@ void JavaScriptDialogManager::RunJavaScriptDialog(
               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.

[Avi (use Gerrit), 2016/02/11 15:55:04]

Wellll... not necessarily. Imagine a calendar tab where the user suppressed
dialogs but which was left open for a month. It could legitimately hit 100
suppressions, and not unreasonably.

If you wanted to go crazy, you totally could track suppressions over time and
cap it when it hits a certain velocity.

In any case, I'm certainly not going to hold the CL over that. I hate dialogs,
so this is more than good enough for me.

+    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;
   }