Store, use and send etags.

media/blink/resource_multibuffer_data_provider.cc

Index: media/blink/resource_multibuffer_data_provider.cc
diff --git a/media/blink/resource_multibuffer_data_provider.cc b/media/blink/resource_multibuffer_data_provider.cc
index 511b356cfe791352c14e119d58d68004f9ec7cb2..283c264469420b33db9726ad23d4fb7a8da2b3d9 100644
--- a/media/blink/resource_multibuffer_data_provider.cc
+++ b/media/blink/resource_multibuffer_data_provider.cc
@@ -84,6 +84,11 @@ void ResourceMultiBufferDataProvider::Start() {
       WebString::fromUTF8(
           net::HttpByteRange::RightUnbounded(byte_pos()).GetHeaderValue()));
 
+  if (!url_data_->etag().empty()) {
+    request.setHTTPHeaderField(WebString::fromUTF8("If-Match"),
+                               WebString::fromUTF8(url_data_->etag()));
+  }
+
   url_data_->frame()->setReferrerForRequest(request, blink::WebURL());
 
   // Disable compression, compression for audio/video doesn't make sense...
@@ -241,6 +246,9 @@ void ResourceMultiBufferDataProvider::didReceiveResponse(
     destination_url_data->set_last_modified(last_modified);
   }
 
+  destination_url_data->set_etag(
+      response.httpHeaderField("ETag").utf8().data());
+
   destination_url_data->set_valid_until(base::Time::Now() +
                                         GetCacheValidUntil(response));