Use a matcher in privacy_budget_browsertest.

This makes the expectations more declarative, and makes it easier to
express more complicated invariants.

Note that in the previous implementation,
kV8Screen_Height_AttributeGetter was listed twice among the expected
keys, but the test did not verify that the |metrics| map contained two
such keys (not that that is possible). |IsSupersetOf| is built on the
idea of a multiset, so it does support checking for repeated expected
elements.

Change-Id: Ia2d617ed826b023bd67f5352e7094fd1136a6e45
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2480964Reviewed-by: Asanka Herath <asanka@chromium.org>
Commit-Queue: Chris Fredrickson <cfredric@google.com>
Cr-Commit-Position: refs/heads/master@{#819125}

chrome/browser/privacy_budget/privacy_budget_browsertest.cc

@@ -13,6 +13,7 @@
 #include "content/public/test/browser_test.h"
 #include "content/public/test/browser_test_utils.h"
 #include "services/metrics/public/cpp/ukm_builders.h"
+#include "testing/gmock/include/gmock/gmock-matchers.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/blink/public/common/privacy_budget/identifiability_study_settings.h"
 #include "third_party/blink/public/common/privacy_budget/identifiable_surface.h"
@@ -26,6 +27,15 @@
 
 namespace {
 
+using testing::IsSupersetOf;
+using testing::Key;
+
+uint64_t HashFeature(const blink::mojom::WebFeature& feature) {
+  return blink::IdentifiableSurface::FromTypeAndToken(
+             blink::IdentifiableSurface::Type::kWebFeature, feature)
+      .ToUkmMetricHash();
+}
+
 // This test runs on Android as well as desktop platforms.
 class PrivacyBudgetBrowserTest : public PlatformBrowserTest {
  public:
@@ -91,22 +101,23 @@ IN_PROC_BROWSER_TEST_F(PrivacyBudgetBrowserTest, SamplingScreenAPIs) {
   // Shouldn't be more than one source here. If this changes, then we'd need to
   // adjust this test to deal.
   ASSERT_EQ(1u, merged_entries.size());
-  const auto& metrics = merged_entries.begin()->second->metrics;
 
   // All of the following features should be included in the list of returned
   // metrics here. The exact values depend on the test host.
-  for (auto feature :
-       {blink::mojom::WebFeature::kV8Screen_Height_AttributeGetter,
-        blink::mojom::WebFeature::kV8Screen_Width_AttributeGetter,
-        blink::mojom::WebFeature::kV8Screen_AvailLeft_AttributeGetter,
-        blink::mojom::WebFeature::kV8Screen_AvailTop_AttributeGetter,
-        blink::mojom::WebFeature::kV8Screen_AvailWidth_AttributeGetter,
-        blink::mojom::WebFeature::kV8Screen_Height_AttributeGetter}) {
-    EXPECT_TRUE(metrics.contains(
-        blink::IdentifiableSurface::FromTypeAndToken(
-            blink::IdentifiableSurface::Type::kWebFeature, feature)
-            .ToUkmMetricHash()));
-  }
+  EXPECT_THAT(
+      merged_entries.begin()->second->metrics,
+      IsSupersetOf({
+          Key(HashFeature(
+              blink::mojom::WebFeature::kV8Screen_Height_AttributeGetter)),
+          Key(HashFeature(
+              blink::mojom::WebFeature::kV8Screen_Width_AttributeGetter)),
+          Key(HashFeature(
+              blink::mojom::WebFeature::kV8Screen_AvailLeft_AttributeGetter)),
+          Key(HashFeature(
+              blink::mojom::WebFeature::kV8Screen_AvailTop_AttributeGetter)),
+          Key(HashFeature(
+              blink::mojom::WebFeature::kV8Screen_AvailWidth_AttributeGetter)),
+      }));
 }
 
 #if BUILDFLAG(FIELDTRIAL_TESTING_ENABLED)