Reset metrics if cellular uploads logic should be applied.

In order to avoid large quantity of uploads after always enabling cellular uploads on Android reset metrics. This should happen only once.

BUG=455847

Review URL: https://codereview.chromium.org/1130993005

Cr-Commit-Position: refs/heads/master@{#329661}

chrome/browser/metrics/chrome_metrics_service_client.cc

@@ -101,8 +101,24 @@ bool IsCellularLogicEnabled() {
       net::NetworkChangeNotifier::GetConnectionType());
 }
 
+// Checks whether it is the first time that cellular uploads logic should be
+// enabled based on whether the the preference for that logic is initialized.
+// This should happen only once as the used preference will be initialized
+// afterwards in |UmaSessionStats.java|.
+bool ShouldClearSavedMetrics() {
+#if defined(OS_ANDROID)
+  PrefService* local_state = g_browser_process->local_state();
+  return !local_state->HasPrefPath(prefs::kMetricsReportingEnabled) &&
+         variations::GetVariationParamValue("UMA_EnableCellularLogUpload",
+                                            "Enabled") == "true";
+#else
+  return false;
+#endif
+}
+
 }  // namespace
 
+
 ChromeMetricsServiceClient::ChromeMetricsServiceClient(
     metrics::MetricsStateManager* state_manager)
     : metrics_state_manager_(state_manager),
@@ -279,6 +295,15 @@ void ChromeMetricsServiceClient::LogPluginLoadingError(
 }
 
 void ChromeMetricsServiceClient::Initialize() {
+  // Clear metrics reports if it is the first time cellular upload logic should
+  // apply to avoid sudden bulk uploads. It needs to be done before initializing
+  // metrics service so that metrics log manager is initialized correctly.
+  if (ShouldClearSavedMetrics()) {
+    PrefService* local_state = g_browser_process->local_state();
+    local_state->ClearPref(metrics::prefs::kMetricsInitialLogs);
+    local_state->ClearPref(metrics::prefs::kMetricsOngoingLogs);
+  }
+
   metrics_service_.reset(new metrics::MetricsService(
       metrics_state_manager_, this, g_browser_process->local_state()));
 
@@ -363,6 +388,12 @@ void ChromeMetricsServiceClient::Initialize() {
       scoped_ptr<metrics::MetricsProvider>(
           SigninStatusMetricsProvider::CreateInstance()));
 #endif  // !defined(OS_CHROMEOS) && !defined(OS_IOS)
+
+  // Clear stability metrics if it is the first time cellular upload logic
+  // should apply to avoid sudden bulk uploads. It needs to be done after all
+  // providers are registered.
+  if (ShouldClearSavedMetrics())
+    metrics_service_->ClearSavedStabilityMetrics();
 }
 
 void ChromeMetricsServiceClient::OnInitTaskGotHardwareClass() {