Centralize the Data Reduction Proxy pass through header

components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h

Index: components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h
diff --git a/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h b/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h
index 2415143b978de1edd9351cf5baaad0f3d189b844..d65f8e2e76fee08c8e460f77ac22feec2fbe0abd 100644
--- a/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h
+++ b/components/data_reduction_proxy/core/common/data_reduction_proxy_headers.h
@@ -68,6 +68,11 @@ struct DataReductionProxyInfo {
 // Gets the header used for data reduction proxy requests and responses.
 const char* chrome_proxy_header();
 
+// The header used to request a data reduction proxy pass through. When a
+// request is sent to the data reduction proxy with this header, it will respond
+// with the original uncompressed response.
+const char* chrome_proxy_pass_through_header();
+
 // Gets the chrome-proxy-ect request header that includes the effective
 // connection type.
 const char* chrome_proxy_ect_header();
@@ -90,10 +95,6 @@ const char* lite_page_directive();
 // compressed video.
 const char* compressed_video_directive();
 
-// Gets the directive used by the data reduction proxy to request that
-// a resource not be transformed.
-const char* identity_directive();
-
 // Gets the Chrome-Proxy directive used by data reduction proxy lite page
 // preview requests and responses.
 const char* chrome_proxy_lite_page_directive();