Revert 89532 - Not allow compression when requesting multimedia

net/url_request/url_request_http_job.cc

Index: net/url_request/url_request_http_job.cc
===================================================================
--- net/url_request/url_request_http_job.cc	(revision 89545)
+++ net/url_request/url_request_http_job.cc	(working copy)
@@ -398,66 +398,56 @@
 }
 
 void URLRequestHttpJob::AddExtraHeaders() {
-  // Supply Accept-Encoding field only if it is not already provided.
-  // It should be provided IF the content is known to have restrictions on
-  // potential encoding, such as streaming multi-media.
-  // For details see bug 47381.
-  // TODO(jar, enal): jpeg files etc. should set up a request header if
-  // possible. Right now it is done only by buffered_resource_loader and
-  // simple_data_source.
-  if (!request_info_.extra_headers.HasHeader(
-      HttpRequestHeaders::kAcceptEncoding)) {
-    bool advertise_sdch = SdchManager::Global() &&
-        SdchManager::Global()->IsInSupportedDomain(request_->url());
-    std::string avail_dictionaries;
-    if (advertise_sdch) {
-      SdchManager::Global()->GetAvailDictionaryList(request_->url(),
-                                                    &avail_dictionaries);
+  // TODO(jar): Consider optimizing away SDCH advertising bytes when the URL is
+  // probably an img or such (and SDCH encoding is not likely).
+  bool advertise_sdch = SdchManager::Global() &&
+      SdchManager::Global()->IsInSupportedDomain(request_->url());
+  std::string avail_dictionaries;
+  if (advertise_sdch) {
+    SdchManager::Global()->GetAvailDictionaryList(request_->url(),
+                                                  &avail_dictionaries);
 
-      // The AllowLatencyExperiment() is only true if we've successfully done a
-      // full SDCH compression recently in this browser session for this host.
-      // Note that for this path, there might be no applicable dictionaries,
-      // and hence we can't participate in the experiment.
-      if (!avail_dictionaries.empty() &&
-          SdchManager::Global()->AllowLatencyExperiment(request_->url())) {
-        // We are participating in the test (or control), and hence we'll
-        // eventually record statistics via either SDCH_EXPERIMENT_DECODE or
-        // SDCH_EXPERIMENT_HOLDBACK, and we'll need some packet timing data.
-        packet_timing_enabled_ = true;
-        if (base::RandDouble() < .01) {
-          sdch_test_control_ = true;  // 1% probability.
-          advertise_sdch = false;
-        } else {
-          sdch_test_activated_ = true;
-        }
+    // The AllowLatencyExperiment() is only true if we've successfully done a
+    // full SDCH compression recently in this browser session for this host.
+    // Note that for this path, there might be no applicable dictionaries, and
+    // hence we can't participate in the experiment.
+    if (!avail_dictionaries.empty() &&
+        SdchManager::Global()->AllowLatencyExperiment(request_->url())) {
+      // We are participating in the test (or control), and hence we'll
+      // eventually record statistics via either SDCH_EXPERIMENT_DECODE or
+      // SDCH_EXPERIMENT_HOLDBACK, and we'll need some packet timing data.
+      packet_timing_enabled_ = true;
+      if (base::RandDouble() < .01) {
+        sdch_test_control_ = true;  // 1% probability.
+        advertise_sdch = false;
+      } else {
+        sdch_test_activated_ = true;
       }
     }
+  }
 
-    // Supply Accept-Encoding headers first so that it is more likely that they
-    // will be in the first transmitted packet.  This can sometimes make it
-    // easier to filter and analyze the streams to assure that a proxy has not
-    // damaged these headers.  Some proxies deliberately corrupt Accept-Encoding
-    // headers.
-    if (!advertise_sdch) {
-      // Tell the server what compression formats we support (other than SDCH).
+  // Supply Accept-Encoding headers first so that it is more likely that they
+  // will be in the first transmitted packet.  This can sometimes make it easier
+  // to filter and analyze the streams to assure that a proxy has not damaged
+  // these headers.  Some proxies deliberately corrupt Accept-Encoding headers.
+  if (!advertise_sdch) {
+    // Tell the server what compression formats we support (other than SDCH).
+    request_info_.extra_headers.SetHeader(
+        HttpRequestHeaders::kAcceptEncoding, "gzip,deflate");
+  } else {
+    // Include SDCH in acceptable list.
+    request_info_.extra_headers.SetHeader(
+        HttpRequestHeaders::kAcceptEncoding, "gzip,deflate,sdch");
+    if (!avail_dictionaries.empty()) {
       request_info_.extra_headers.SetHeader(
-          HttpRequestHeaders::kAcceptEncoding, "gzip,deflate");
-    } else {
-      // Include SDCH in acceptable list.
-      request_info_.extra_headers.SetHeader(
-          HttpRequestHeaders::kAcceptEncoding, "gzip,deflate,sdch");
-      if (!avail_dictionaries.empty()) {
-        request_info_.extra_headers.SetHeader(
-            kAvailDictionaryHeader,
-            avail_dictionaries);
-        sdch_dictionary_advertised_ = true;
-        // Since we're tagging this transaction as advertising a dictionary,
-        // we'll definitely employ an SDCH filter (or tentative sdch filter)
-        // when we get a response.  When done, we'll record histograms via
-        // SDCH_DECODE or SDCH_PASSTHROUGH.  Hence we need to record packet
-        // arrival times.
-        packet_timing_enabled_ = true;
-      }
+          kAvailDictionaryHeader,
+          avail_dictionaries);
+      sdch_dictionary_advertised_ = true;
+      // Since we're tagging this transaction as advertising a dictionary, we'll
+      // definitely employ an SDCH filter (or tentative sdch filter) when we get
+      // a response.  When done, we'll record histograms via SDCH_DECODE or
+      // SDCH_PASSTHROUGH.  Hence we need to record packet arrival times.
+      packet_timing_enabled_ = true;
     }
   }