Initial CL for Downloads resumption.

content/browser/download/download_resource_handler.cc

Index: content/browser/download/download_resource_handler.cc
diff --git a/content/browser/download/download_resource_handler.cc b/content/browser/download/download_resource_handler.cc
index 4498c986e89f9cce154abc88b864fb6e5728a0eb..59196d388b6fad70fd20630bce5b845049b82740 100644
--- a/content/browser/download/download_resource_handler.cc
+++ b/content/browser/download/download_resource_handler.cc
@@ -73,10 +73,12 @@ static void StartOnUIThread(
 }  // namespace
 
 DownloadResourceHandler::DownloadResourceHandler(
+    DownloadId id,
     net::URLRequest* request,
     const DownloadResourceHandler::OnStartedCallback& started_cb,
     scoped_ptr<DownloadSaveInfo> save_info)
-    : render_view_id_(0),               // Actually initialized below.
+    : download_id_(id),
+      render_view_id_(0),               // Actually initialized below.
       content_length_(0),
       request_(request),
       started_cb_(started_cb),
@@ -149,6 +151,7 @@ bool DownloadResourceHandler::OnResponseStarted(
   stream_writer_->RegisterCallback(
       base::Bind(&DownloadResourceHandler::ResumeRequest, AsWeakPtr()));
 
+  info->download_id = download_id_;
   info->url_chain = request_->url_chain();
   info->referrer_url = GURL(request_->referrer());
   info->start_time = base::Time::Now();
@@ -173,6 +176,14 @@ bool DownloadResourceHandler::OnResponseStarted(
       info->last_modified = last_modified_hdr;
     if (headers->EnumerateHeader(NULL, "ETag", &etag))
       info->etag = etag;
+
+    int status = headers->response_code();
+    if (status == 200) {  // Continue with download:
+      // Downloading the full file.  If we asked for a range, we didn't
+      // get it--reset the file pointers to reflect that.
+      save_info_->offset = 0;
+      save_info_->hash_state = "";
+    }
   }
 
   std::string content_type_header;
@@ -323,19 +334,31 @@ bool DownloadResourceHandler::OnResponseCompleted(
     reason = DOWNLOAD_INTERRUPT_REASON_USER_CANCELED;
   }
 
-  if (status.is_success()) {
-    if (response_code >= 400) {
+  if (status.is_success() &&
+      (reason == DOWNLOAD_INTERRUPT_REASON_NONE) &&
+      request_->response_headers()) {
+    // Handle server's response codes.
+    if ((response_code >= 0) && ((response_code % 100) != 2)) {
       switch(response_code) {
-        case 404:  // File Not Found.
+        // Continue with download:
+        case 200:   // Downloading the full file, even if we asked for a
+                    // range.
+        case 206:   // Partial content.  Leave alone.
+          break;
+        case 204:   // No content.  File not present.
+        case 404:   // File Not Found.
           reason = DOWNLOAD_INTERRUPT_REASON_SERVER_BAD_CONTENT;
           break;
+        case 412:   // Precondition failed.  Fails 'If-Unmodified-Since' or
+                    // 'If-Match'.
+          reason = DOWNLOAD_INTERRUPT_REASON_SERVER_PRECONDITION;
+          break;
         case 416:  // Range Not Satisfiable.
+          // Retry by downloading from the start automatically:
+          // If we haven't received data when we get this error, we won't.
           reason = DOWNLOAD_INTERRUPT_REASON_SERVER_NO_RANGE;
           break;
-        case 412:  // Precondition Failed.
-          reason = DOWNLOAD_INTERRUPT_REASON_SERVER_PRECONDITION;
-          break;
-        default:
+        default:    // All other errors.
           reason = DOWNLOAD_INTERRUPT_REASON_SERVER_FAILED;
           break;
       }