components/image_fetcher: Add a from_http_cache flag to RequestMetadata

components/image_fetcher/request_metadata.h

Index: components/image_fetcher/request_metadata.h
diff --git a/components/image_fetcher/request_metadata.h b/components/image_fetcher/request_metadata.h
index 6b41e2d3c3136efc7fb600b37a522685a751d4db..03963eeb687a7ea1328b8cc564b09adf614027ba 100644
--- a/components/image_fetcher/request_metadata.h
+++ b/components/image_fetcher/request_metadata.h
@@ -7,13 +7,23 @@
 
 #include <string>
 
+#include "net/url_request/url_fetcher.h"
+
 namespace image_fetcher {
 
 // Metadata for a URL request.
 struct RequestMetadata {
+  // Impossible http response code. Used to signal that no http response code
+  // was received.
+  enum ResponseCode {
+    RESPONSE_CODE_INVALID = net::URLFetcher::RESPONSE_CODE_INVALID
+  };
+
+  RequestMetadata();
+
   std::string mime_type;
-  // HTTP response code.
-  int response_code;
+  int http_response_code;
+  bool from_http_cache;
 };
 
 bool operator==(const RequestMetadata& lhs, const RequestMetadata& rhs);