AW UMA: refactor package name sampling

This moves the package name sampling result into a boolean member
variable (which slightly improves performance, and is more consistent
with is_in_sample_), and rephrases a comment.

This fixes some tests to mock the IsInPackageNameSample() value prior to
MaybeStartMetrics, rather than after, since the value is cached during
that method.

This is a follow up to feedback on https://crrev.com/c/1898711.

Test: run_android_webview_unittests --gtest_filter=AwMetricsServiceClientTest.*
Change-Id: I824540aa7362ab34f9cb4981b88cc446338bdff3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1937704Reviewed-by: Tao Bai <michaelbai@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719429}

android_webview/browser/metrics/aw_metrics_service_client.cc

@@ -59,7 +59,7 @@ const double kStableSampledInRate = 0.02;
 const double kBetaDevCanarySampledInRate = 0.99;
 
 // As a mitigation to preserve use privacy, the privacy team has asked that we
-// upload package name with no more than 10% of UMA records. This is to mitigate
+// upload package name with no more than 10% of UMA clients. This is to mitigate
 // fingerprinting for users on low-usage applications (if an app only has a
 // a small handful of users, there's a very good chance many of them won't be
 // uploading UMA records due to sampling). Do not change this constant without
@@ -190,6 +190,7 @@ void AwMetricsServiceClient::MaybeStartMetrics() {
       RegisterForNotifications();
       metrics_state_manager_->ForceClientIdCreation();
       is_in_sample_ = IsInSample();
+      is_in_package_name_sample_ = IsInPackageNameSample();
       if (IsReportingEnabled()) {
         // WebView has no shutdown sequence, so there's no need for a matching
         // Stop() call.
@@ -327,7 +328,7 @@ bool AwMetricsServiceClient::ShouldStartUpFastForTesting() const {
 }
 
 std::string AwMetricsServiceClient::GetAppPackageName() {
-  if (IsInPackageNameSample() && CanRecordPackageNameForAppType()) {
+  if (is_in_package_name_sample_ && CanRecordPackageNameForAppType()) {
     JNIEnv* env = base::android::AttachCurrentThread();
     base::android::ScopedJavaLocalRef<jstring> j_app_name =
         Java_AwMetricsServiceClient_getAppPackageName(env);

android_webview/browser/metrics/aw_metrics_service_client.h

@@ -185,6 +185,7 @@ class AwMetricsServiceClient : public metrics::MetricsServiceClient,
   bool user_consent_ = false;
   bool app_consent_ = false;
   bool is_in_sample_ = false;
+  bool is_in_package_name_sample_ = false;
   bool fast_startup_for_testing_ = false;
 
   // When non-zero, this overrides the default value in

android_webview/browser/metrics/aw_metrics_service_client_unittest.cc

@@ -179,9 +179,9 @@ TEST_F(AwMetricsServiceClientTest, TestShouldNotUploadPackageName_AppType) {
   auto prefs = CreateTestPrefs();
   prefs->SetString(metrics::prefs::kMetricsClientID, kTestClientId);
   auto client = CreateAndInitTestClient(prefs.get());
-  client->SetHaveMetricsConsent(true, true);
   client->SetRecordPackageNameForAppType(false);
   client->SetInPackageNameSample(true);
+  client->SetHaveMetricsConsent(true, true);
   std::string package_name = client->GetAppPackageName();
   EXPECT_TRUE(package_name.empty());
 }
@@ -190,9 +190,9 @@ TEST_F(AwMetricsServiceClientTest, TestShouldNotUploadPackageName_SampledOut) {
   auto prefs = CreateTestPrefs();
   prefs->SetString(metrics::prefs::kMetricsClientID, kTestClientId);
   auto client = CreateAndInitTestClient(prefs.get());
-  client->SetHaveMetricsConsent(true, true);
   client->SetRecordPackageNameForAppType(true);
   client->SetInPackageNameSample(false);
+  client->SetHaveMetricsConsent(true, true);
   std::string package_name = client->GetAppPackageName();
   EXPECT_TRUE(package_name.empty());
 }
@@ -201,9 +201,9 @@ TEST_F(AwMetricsServiceClientTest, TestCanUploadPackageName) {
   auto prefs = CreateTestPrefs();
   prefs->SetString(metrics::prefs::kMetricsClientID, kTestClientId);
   auto client = CreateAndInitTestClient(prefs.get());
-  client->SetHaveMetricsConsent(true, true);
   client->SetRecordPackageNameForAppType(true);
   client->SetInPackageNameSample(true);
+  client->SetHaveMetricsConsent(true, true);
   std::string package_name = client->GetAppPackageName();
   EXPECT_FALSE(package_name.empty());
 }