[PageLoadMetrics] Reenable AdsMetrics and handle case where navigation aborts

chrome/browser/page_load_metrics/observers/ads_page_load_metrics_observer_browsertest.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <string>
+
+#include "base/macros.h"
+#include "base/test/histogram_tester.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "chrome/test/base/ui_test_utils.h"
+#include "content/public/test/browser_test.h"
+#include "content/public/test/browser_test_utils.h"
+#include "net/test/embedded_test_server/embedded_test_server.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "url/gurl.h"
+
+class AdsPageLoadMetricsObserverBrowserTest : public InProcessBrowserTest {
+ public:
+  AdsPageLoadMetricsObserverBrowserTest() {}
+  ~AdsPageLoadMetricsObserverBrowserTest() override {}
+
+  void SetUpOnMainThread() override {
+    ASSERT_TRUE(embedded_test_server()->Start());
+    InProcessBrowserTest::SetUpOnMainThread();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AdsPageLoadMetricsObserverBrowserTest);
+};
+
+// Test that a subframe that aborts (due to doc.write) doesn't cause a crash
+// if it continues to load resources.
+IN_PROC_BROWSER_TEST_F(AdsPageLoadMetricsObserverBrowserTest,
+                       DocOverwritesNavigation) {
+  content::DOMMessageQueue msg_queue;
+
+  base::HistogramTester histogram_tester;
+
+  ui_test_utils::NavigateToURL(
+      browser(), embedded_test_server()->GetURL(
+                     "/ads_observer/docwrite_provisional_frame.html"));
+  std::string status;
+  EXPECT_TRUE(msg_queue.WaitForMessage(&status));
+  EXPECT_EQ("\"loaded\"", status);
+
+  // Navigate away to force the histogram recording.
+  ui_test_utils::NavigateToURL(browser(), GURL(url::kAboutBlankURL));
+
+  histogram_tester.ExpectUniqueSample(
+      "PageLoad.Clients.Ads.Google.FrameCounts.AnyParentFrame.AdFrames", 1, 1);
+  histogram_tester.ExpectUniqueSample(
+      "PageLoad.Clients.Ads.Google.Bytes.AdFrames.Aggregate.Total",
+      0 /* < 1 KB */, 1);
+}