[ImageFetcher] Return http response headers

components/image_fetcher/core/request_metadata.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/image_fetcher/core/request_metadata.h"
 
+#include "net/http/http_response_headers.h"
+
 namespace image_fetcher {
 
+namespace {
+
+bool HttpHeadersEqual(const net::HttpResponseHeaders* lhs,
+                      const net::HttpResponseHeaders* rhs) {
+  if (!lhs && !rhs) {
+    return true;  // Equal if both nullptr.
+  }
+  if (!lhs || !rhs) {
+    return false;  // We cannot compare the content if one of them is nullptr.
+  }
+  return lhs->raw_headers() == rhs->raw_headers();
+}
+
+}  // namespace
+
 RequestMetadata::RequestMetadata()
-    : http_response_code(RESPONSE_CODE_INVALID), from_http_cache(false) {}
+    : http_response_code(RESPONSE_CODE_INVALID),
+      from_http_cache(false),
+      http_response_headers(nullptr) {}
 
 bool operator==(const RequestMetadata& lhs, const RequestMetadata& rhs) {
   return lhs.mime_type == rhs.mime_type &&
          lhs.http_response_code == rhs.http_response_code &&
-         lhs.from_http_cache == rhs.from_http_cache;
+         lhs.from_http_cache == rhs.from_http_cache &&
+         HttpHeadersEqual(lhs.http_response_headers, rhs.http_response_headers);
 }
 
 bool operator!=(const RequestMetadata& lhs, const RequestMetadata& rhs) {
   return !(lhs == rhs);
 }
 
 }  // namespace image_fetcher