WebView: Persist unsent log.

Test manually, the persisted log loaded at next startup.

Bug: 1076549
Change-Id: Ibfc273431b8ccd313435b55bdb1889b7c5913045
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2173960Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Michael Bai <michaelbai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808588}

android_webview/browser/aw_feature_list_creator.cc

@@ -74,6 +74,9 @@ const char* const kPersistentPrefsAllowlist[] = {
     metrics::prefs::kStabilityRendererHangCount,
     metrics::prefs::kStabilityRendererLaunchCount,
     metrics::prefs::kUninstallMetricsPageLoadCount,
+    // Unsent logs.
+    metrics::prefs::kMetricsInitialLogs,
+    metrics::prefs::kMetricsOngoingLogs,
     // Unsent logs metadata.
     metrics::prefs::kMetricsInitialLogsMetadata,
     metrics::prefs::kMetricsOngoingLogsMetadata,