Add PDFExtensionTest.Metrics.

Verify the PDF plugin can successfully report metrics. Currently, the
plugin reports metrics using the PPAPI interface, but that will change
in the future. Make sure metrics continue to work, and help prevent
issues like https://crbug.com/1043019 from happening.

Change-Id: I0306247a320040231b8f47a4981a45fcff689ec4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2119204
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753474}

chrome/browser/pdf/pdf_extension_test.cc

@@ -22,6 +22,8 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/lock.h"
 #include "base/task/post_task.h"
+#include "base/test/metrics/histogram_tester.h"
+#include "base/test/metrics/user_action_tester.h"
 #include "base/test/test_timeouts.h"
 #include "base/thread_annotations.h"
 #include "base/threading/thread_restrictions.h"
@@ -31,6 +33,7 @@
 #include "chrome/browser/extensions/component_loader.h"
 #include "chrome/browser/extensions/extension_apitest.h"
 #include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/metrics/subprocess_metrics_provider.h"
 #include "chrome/browser/pdf/pdf_extension_test_util.h"
 #include "chrome/browser/pdf/pdf_extension_util.h"
 #include "chrome/browser/plugins/plugin_prefs.h"
@@ -2344,6 +2347,32 @@ IN_PROC_BROWSER_TEST_F(PDFExtensionTest,
   ASSERT_TRUE(LoadPdf(test_pdf_url));
 }
 
+IN_PROC_BROWSER_TEST_F(PDFExtensionTest, Metrics) {
+  base::HistogramTester histograms;
+  base::UserActionTester actions;
+
+  GURL test_pdf_url(embedded_test_server()->GetURL("/pdf/combobox_form.pdf"));
+  WebContents* guest_contents = LoadPdfGetGuestContents(test_pdf_url);
+  ASSERT_TRUE(guest_contents);
+
+  SubprocessMetricsProvider::MergeHistogramDeltasForTesting();
+
+  // Histograms.
+  // Duplicating some constants to avoid reaching into pdf/ internals.
+  constexpr int kLoadedDocument = 0;
+  constexpr int kAcroForm = 1;
+  histograms.ExpectUniqueSample("PDF.DocumentFeature", kLoadedDocument, 1);
+  histograms.ExpectUniqueSample("PDF.FormType", kAcroForm, 1);
+  histograms.ExpectUniqueSample("PDF.IsTagged", 0, 1);
+  histograms.ExpectUniqueSample("PDF.HasAttachment", 0, 1);
+
+  // Custom histograms.
+  histograms.ExpectUniqueSample("PDF.PageCount", 1, 1);
+
+  // User actions.
+  EXPECT_EQ(1, actions.GetActionCount("PDF.LoadSuccess"));
+}
+
 // This test suite does a simple text-extraction based on the accessibility
 // internals, breaking lines & paragraphs where appropriate.  Unlike
 // TreeDumpTests, this allows us to verify the kNextOnLine and kPreviousOnLine