Component updater on-demand logic with ResourceThrottle

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

Index: chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc
===================================================================
--- chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc	(revision 231370)
+++ chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc	(working copy)
@@ -9,8 +9,10 @@
 #include "base/base64.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
+#include "base/strings/string_util.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
+#include "chrome/browser/component_updater/component_updater_service.h"
 #include "chrome/browser/content_settings/host_content_settings_map.h"
 #include "chrome/browser/download/download_request_limiter.h"
 #include "chrome/browser/download/download_resource_throttle.h"
@@ -193,6 +195,30 @@
   }
 }
 
+void AppendComponentUpaterThrottles(

[Sorin Jianu, 2013/10/30 21:02:44]

Updater

[cpu_(ooo_6.6-7.5), 2013/10/31 04:38:26]

Done.

+    net::URLRequest* request,
+    content::ResourceContext* resource_context,
+    ResourceType::Type resource_type,
+    ScopedVector<content::ResourceThrottle>* throttles) {
+  char* crx_id = NULL;
+  // Check for PNaCL nexe request.
+  if (resource_type == ResourceType::OBJECT) {
+    const net::HttpRequestHeaders& headers = request->extra_request_headers();
+    std::string accept_headers;
+    if (headers.GetHeader("Accept", &accept_headers)) {
+      if (accept_headers.find("application/x-pnacl") != std::string::npos)
+        crx_id = "hnimpnehoodheedghdeeijklkeaacbdc";
+    }
+  }
+
+  if (crx_id) {
+    // We got a component we need to install, so throttle the resource
+    // until the component is installed.
+    ComponentUpdateService* cus = g_browser_process->component_updater();
+    throttles->push_back(cus->GetResourceThrottle(request, crx_id));
+  }
+}
+
 }  // end namespace
 
 ChromeResourceDispatcherHostDelegate::ChromeResourceDispatcherHostDelegate(
@@ -319,6 +345,12 @@
                                   resource_context,
                                   resource_type,
                                   throttles);
+  if (!is_prerendering) {

[waffles, 2013/10/30 21:11:20]

I don't know too much about prerendering; will our system break if we prerender
a page that requires some component resource, and then the user navigates to
that page? We don't re-render it, I presume, so will we have missed the request
that we can throttle?

[cpu_(ooo_6.6-7.5), 2013/10/30 21:43:05]

Your question is very interesting.

Pre-rendering avoids fetching most things that cause perceivable behavior such
as video/audio/extensions/plugins/etc.

So while possible that a corner case slips by the opposite case is worse because
we clog the pipes and since we end up discarding most of the pre-renderings
anyway it is a wasted effort.

I'll ask Darin to make sure this is the right tradeoff.

+    AppendComponentUpaterThrottles(request,
+                                   resource_context,
+                                   resource_type,
+                                   throttles);
+  }
 
   if (io_data->resource_prefetch_predictor_observer()) {
     io_data->resource_prefetch_predictor_observer()->OnRequestStarted(