Add Brotli to Accept Encoding header for secure DRP requests

components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc

Index: components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
diff --git a/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc b/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
index 84f14ecf4198c00414f0d61c1c203c517ce6ae95..b5cb91740cd8926f96cffa3e4843ad8866c61451 100644
--- a/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
+++ b/components/data_reduction_proxy/core/common/data_reduction_proxy_params.cc
@@ -230,6 +230,16 @@ bool IsZeroRttQuicEnabled() {
              params, "enable_zero_rtt", "false") == "true";
 }
 
+bool IsBrotliAcceptEncodingEnabled() {
+  // Brotli encoding is enabled by default since the data reduction proxy server
+  // controls when to serve Brotli encoded content. It can be disabled in
+  // Chromium only if Chromium belongs to a field trial group whose name starts
+  // with "Disabled".
+  return !base::StartsWith(base::FieldTrialList::FindFullName(
+                               "DataReductionProxyBrotliAcceptEncoding"),
+                           kDisabled, base::CompareCase::SENSITIVE);
+}
+
 bool IsConfigClientEnabled() {
   // Config client is enabled by default. It can be disabled only if Chromium
   // belongs to a field trial group whose name starts with "Disabled".