Revert of Cleanup DataReductionProxy (DRP) Brotli code

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 d2991d7df16679a63a812276421bb489c34afa91..d4f6ae26af03f4a97316ffbc0b7e5f5bbc136cb6 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
@@ -85,15 +85,9 @@
 }
 
 void DataReductionProxyRequestOptions::Init() {
-  DCHECK(thread_checker_.CalledOnValidThread());
   key_ = GetDefaultKey(),
   UpdateCredentials();
   UpdateExperiments();
-}
-
-std::string DataReductionProxyRequestOptions::GetHeaderValueForTesting() const {
-  DCHECK(thread_checker_.CalledOnValidThread());
-  return header_value_;
 }
 
 void DataReductionProxyRequestOptions::UpdateExperiments() {
@@ -139,19 +133,16 @@
 }
 
 base::Time DataReductionProxyRequestOptions::Now() const {
-  DCHECK(thread_checker_.CalledOnValidThread());
   return base::Time::Now();
 }
 
 void DataReductionProxyRequestOptions::RandBytes(void* output,
                                                  size_t length) const {
-  DCHECK(thread_checker_.CalledOnValidThread());
   crypto::RandBytes(output, length);
 }
 
 void DataReductionProxyRequestOptions::AddRequestHeader(
     net::HttpRequestHeaders* request_headers) {
-  DCHECK(thread_checker_.CalledOnValidThread());
   base::Time now = Now();
   // Authorization credentials must be regenerated if they are expired.
   if (!use_assigned_credentials_ && (now > credentials_expiration_time_))
@@ -216,12 +207,10 @@
 }
 
 void DataReductionProxyRequestOptions::Invalidate() {
-  DCHECK(thread_checker_.CalledOnValidThread());
   SetSecureSession(std::string());
 }
 
 std::string DataReductionProxyRequestOptions::GetDefaultKey() const {
-  DCHECK(thread_checker_.CalledOnValidThread());
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   std::string key =