Add Accept-Encoding: br for secure data reduction proxy requests.

components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.cc

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.cc
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.cc b/components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.cc
index 7f0382e235b503e74ba94d764af4f086d069b65b..057ac1cd51d46d848d35345266581c6dab064632 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.cc
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_request_options.cc
@@ -23,8 +23,10 @@
 #include "crypto/random.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/load_flags.h"
+#include "net/http/http_request_headers.h"
 #include "net/proxy/proxy_server.h"
 #include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context.h"
 
 #if defined(USE_GOOGLE_API_KEYS_FOR_AUTH_KEY)
 #include "google_apis/google_api_keys.h"
@@ -37,6 +39,17 @@ std::string FormatOption(const std::string& name, const std::string& value) {
   return name + "=" + value;
 }
 
+bool HasBrotliAcceptEncoding(base::StringPiece accept_encoding_header) {
+  for (base::StringPiece encoding : base::SplitStringPiece(
+           accept_encoding_header, ",", base::TRIM_WHITESPACE,
+           base::SPLIT_WANT_NONEMPTY)) {
+    if (encoding == "br") {
+      return true;
+    }
+  }
+  return false;
+}
+
 }  // namespace
 
 const char kSessionHeaderOption[] = "ps";
@@ -154,6 +167,24 @@ void DataReductionProxyRequestOptions::AddRequestHeader(
   request_headers->SetHeader(kChromeProxyHeader, header_value);
 }
 
+void DataReductionProxyRequestOptions::AddBrotliAcceptEncoding(
+    const net::URLRequest& request,
+    net::HttpRequestHeaders* request_headers) {
+  std::string accept_encoding_header;
+  if (!request.context()->enable_brotli() ||
+      !request_headers->GetHeader(net::HttpRequestHeaders::kAcceptEncoding,
+                                  &accept_encoding_header) ||
+      HasBrotliAcceptEncoding(accept_encoding_header))
+    return;
+  if (accept_encoding_header.empty()) {
+    accept_encoding_header = "br";
+  } else {
+    accept_encoding_header += ", br";
+  }
+  request_headers->SetHeader(net::HttpRequestHeaders::kAcceptEncoding,
+                             accept_encoding_header);
+}
+
 void DataReductionProxyRequestOptions::ComputeCredentials(
     const base::Time& now,
     std::string* session,