Add DataReductionProxyExperimentsStats and UMA for measuring potentially non-compressed bytes.

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 e6587fc1af857f1b2731c51adaa43312969a3a52..fbdb5cd0be07b8b649e0874b5a344b756f76489b 100644
--- a/android_webview/browser/aw_browser_context.cc
+++ b/android_webview/browser/aw_browser_context.cc
@@ -171,7 +171,8 @@ void AwBrowserContext::PreMainMessageLoopRun() {
       new data_reduction_proxy::DataReductionProxyService(
           scoped_ptr<
               data_reduction_proxy::DataReductionProxyCompressionStats>(),
-          data_reduction_proxy_settings_.get(), GetAwURLRequestContext(),
+          data_reduction_proxy_settings_.get(), nullptr,
+          GetAwURLRequestContext(),
           BrowserThread::GetMessageLoopProxyForThread(BrowserThread::IO)));
   data_reduction_proxy_io_data_->SetDataReductionProxyService(
       data_reduction_proxy_service_->GetWeakPtr());