Save image should download the original image when Data Saver is enabled.

content/browser/android/download_controller_android_impl.cc

Index: content/browser/android/download_controller_android_impl.cc
diff --git a/content/browser/android/download_controller_android_impl.cc b/content/browser/android/download_controller_android_impl.cc
index d8da51836f8b44754b555af927974795d304ffaa..e0cf8ae680ee44ce2a00a91c35eb289cf9f88595 100644
--- a/content/browser/android/download_controller_android_impl.cc
+++ b/content/browser/android/download_controller_android_impl.cc
@@ -390,7 +390,8 @@ DownloadControllerAndroidImpl::JavaObject*
 }
 
 void DownloadControllerAndroidImpl::StartContextMenuDownload(
-    const ContextMenuParams& params, WebContents* web_contents, bool is_link) {
+    const ContextMenuParams& params, WebContents* web_contents, bool is_link,
+    const std::string& headers) {
   const GURL& url = is_link ? params.link_url : params.src_url;
   const GURL& referring_url = params.frame_url.is_empty() ?
       params.page_url : params.frame_url;
@@ -405,7 +406,17 @@ void DownloadControllerAndroidImpl::StartContextMenuDownload(
   dl_params->set_referrer(referrer);
   if (is_link)
     dl_params->set_referrer_encoding(params.frame_charset);
-  else
+  if (!headers.empty()) {
+    std::vector<std::string> key_value_list;
+    base::SplitString(headers, '\n', &key_value_list);

[Ted C, 2015/06/22 20:40:49]

Instead of this, could it use something like
HttpRequestHeaders::AddHeadersFromString?  I was hoping there would be some sort
of shareable logic for this if possible.  (note the \r\n requirement for that
though)

[bengr, 2015/06/22 22:13:10]

Agreed.

[megjablon, 2015/06/22 23:21:02]

I don't see another way to add the headers here other than
DownloadURLParameters::add_request_header. We could modify that or add a
add_request_headers_from_string, but that would just move the splitting logic
elsewhere. web_contents_impl.cc also uses this same strategy to add headers to
DowloadURLParameters.

[Ted C, 2015/06/22 23:25:28]

I was thinking that you would still use
DownloadURLParameters::add_request_header, but HttpRequestHeaders would parse
the string and allows you to iterate over the pair.

i.e.:

net::HttpRequestHeaders headers;
headers.AddHeadersFromString(extra_headers);
for (net::HttpRequestHeaders::Iterator it(headers); it.GetNext();) {
  dl_params->add_request_header(it.name(), it.value());
}

[megjablon, 2015/06/23 00:54:27]

Ah my bad. I misunderstood. Done.

+    for (const auto& key_value : key_value_list) {
+      std::vector<std::string> pair;
+      base::SplitString(key_value, ':', &pair);
+      DCHECK_EQ(2ul, pair.size());
+      dl_params->add_request_header(pair[0], pair[1]);
+    }
+  }
+  if (!is_link && headers.empty())
     dl_params->set_prefer_cache(true);
   dl_params->set_prompt(false);
   dlm->DownloadUrl(dl_params.Pass());