Only show a beforeunload dialog if a frame has had a user gesture since its load.

content/public/test/browser_test_utils.cc

Index: content/public/test/browser_test_utils.cc
diff --git a/content/public/test/browser_test_utils.cc b/content/public/test/browser_test_utils.cc
index 052ffca5772fabc52cc6e6cfd336c9c52f51db39..b9a3011b3e9321b4dd11c57cc67f7c085808a229 100644
--- a/content/public/test/browser_test_utils.cc
+++ b/content/public/test/browser_test_utils.cc
@@ -471,6 +471,18 @@ bool WaitForLoadStop(WebContents* web_contents) {
   return IsLastCommittedEntryOfPageType(web_contents, PAGE_TYPE_NORMAL);
 }
 
+void PrepContentsForBeforeUnloadTest(WebContents* web_contents) {
+  for (auto* frame : web_contents->GetAllFrames()) {
+    // JavaScript onbeforeunload dialogs are ignored unless the frame received a
+    // user gesture. Make sure the frames have user gestures.
+    frame->ExecuteJavaScriptWithUserGestureForTests(base::string16());
+
+    // Disable the hang monitor, otherwise there will be a race between the
+    // beforeunload dialog and the beforeunload hang timer.
+    frame->DisableBeforeUnloadHangMonitorForTesting();
+  }
+}
+
 bool IsLastCommittedEntryOfPageType(WebContents* web_contents,
                                     content::PageType page_type) {
   NavigationEntry* last_entry =