Move the thread hop for UMA user actions from content:: to base::.

android_webview/browser/aw_browser_context.cc

Index: android_webview/browser/aw_browser_context.cc
diff --git a/android_webview/browser/aw_browser_context.cc b/android_webview/browser/aw_browser_context.cc
index 73d840c0f594771fbbeb1723780c9bf5709361b3..07658d31d9acb4c33874bbdf29a943ec29a304f6 100644
--- a/android_webview/browser/aw_browser_context.cc
+++ b/android_webview/browser/aw_browser_context.cc
@@ -18,6 +18,7 @@
 #include "android_webview/common/aw_content_client.h"
 #include "base/base_paths_android.h"
 #include "base/bind.h"
+#include "base/metrics/user_metrics.h"
 #include "base/path_service.h"
 #include "components/autofill/core/common/autofill_pref_names.h"
 #include "components/data_reduction_proxy/core/browser/data_reduction_proxy_compression_stats.h"
@@ -259,6 +260,8 @@ void AwBrowserContext::PreMainMessageLoopRun() {
   const FilePath guid_file_path =
       GetPath().Append(FILE_PATH_LITERAL("metrics_guid"));
 
+  base::SetRecordActionTaskRunner(
+      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::UI));
   AwMetricsServiceClient::GetInstance()->Initialize(
       user_pref_service_.get(),
       content::BrowserContext::GetDefaultStoragePartition(this)->