Include suppressed dialogs in the FineTiming histogram

Review URL: https://codereview.chromium.org/1688183002

Cr-Commit-Position: refs/heads/master@{#374920}
(cherry picked from commit 505f421d0a73adae4f74924b3022996c731de40e)

BUG=588833

Review URL: https://codereview.chromium.org/1732563002 .

Cr-Commit-Position: refs/branch-heads/2623@{#488}
Cr-Branched-From: 92d77538a86529ca35f9220bd3cd512cbea1f086-refs/heads/master@{#369907}

3 files changed, 20 insertions, 1 deletions

diff --git a/components/app_modal/javascript_app_modal_dialog.cc b/components/app_modal/javascript_app_modal_dialog.cc
index d494081..92ee660 100644
--- a/components/app_modal/javascript_app_modal_dialog.cc
+++ b/components/app_modal/javascript_app_modal_dialog.cc
@@ -52,7 +52,8 @@ void EnforceMaxPromptSize(const base::string16& in_string,
 
 ChromeJavaScriptDialogExtraData::ChromeJavaScriptDialogExtraData()
     : has_already_shown_a_dialog_(false),
-      suppress_javascript_messages_(false) {}
+      suppress_javascript_messages_(false),
+      suppressed_dialog_count_(0) {}
 
 JavaScriptAppModalDialog::JavaScriptAppModalDialog(
     content::WebContents* web_contents,
diff --git a/components/app_modal/javascript_app_modal_dialog.h b/components/app_modal/javascript_app_modal_dialog.h
index fca11c2..0fb4d89 100644
--- a/components/app_modal/javascript_app_modal_dialog.h
+++ b/components/app_modal/javascript_app_modal_dialog.h
@@ -25,6 +25,9 @@ class ChromeJavaScriptDialogExtraData {
 
   // True if the user has decided to block future JavaScript dialogs.
   bool suppress_javascript_messages_;
+
+  // Number of dialogs from the origin that were suppressed.
+  int suppressed_dialog_count_;
 };
 
 // A controller + model class for JavaScript alert, confirm, prompt, and
diff --git a/components/app_modal/javascript_dialog_manager.cc b/components/app_modal/javascript_dialog_manager.cc
index 0fcfb92..3dc5516 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;
   }