Add PrerenderResourceHandler and hook it into the ResourceDispatcherHost....

chrome/browser/prerender/prerender_resource_handler.cc

Index: chrome/browser/prerender/prerender_resource_handler.cc
diff --git a/chrome/browser/prerender/prerender_resource_handler.cc b/chrome/browser/prerender/prerender_resource_handler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c015fdc95937be6eb96d5c25659e690614d3e1ec
--- /dev/null
+++ b/chrome/browser/prerender/prerender_resource_handler.cc
@@ -0,0 +1,125 @@
+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/prerender/prerender_resource_handler.h"
+
+#include "chrome/common/resource_response.h"
+#include "net/base/load_flags.h"
+#include "net/http/http_response_headers.h"
+#include "net/url_request/url_request.h"
+
+PrerenderResourceHandler::PrerenderResourceHandler(
+    ResourceHandler* next_handler,
+    PrerenderManager* prerender_manager)
+    : next_handler_(next_handler),
+      prerender_manager_(prerender_manager),
+      ALLOW_THIS_IN_INITIALIZER_LIST(
+          prerender_callback_(NewCallback(
+              this, &PrerenderResourceHandler::StartPrerender))) {
+  DCHECK(next_handler);
+  DCHECK(prerender_manager);
+}
+
+// This constructor is only used from unit tests.
+PrerenderResourceHandler::PrerenderResourceHandler(
+    ResourceHandler* next_handler,
+    PrerenderCallback* callback)
+    : next_handler_(next_handler),
+      prerender_callback_(callback) {
+  DCHECK(next_handler);
+      }

[willchan no longer on Chromium, 2010/12/17 21:45:17]

indentation

[cbentzel, 2010/12/19 00:40:56]

Done.

+
+PrerenderResourceHandler::~PrerenderResourceHandler() {
+}
+
+bool PrerenderResourceHandler::OnUploadProgress(int request_id,
+                                                uint64 position,
+                                                uint64 size) {
+  return next_handler_->OnUploadProgress(request_id, position, size);
+}
+
+bool PrerenderResourceHandler::OnRequestRedirected(int request_id,
+                                                   const GURL& url,
+                                                   ResourceResponse* response,
+                                                   bool* defer) {
+  bool will_redirect = next_handler_->OnRequestRedirected(
+      request_id, url, response, defer);
+  if (will_redirect)
+    url_ = url;
+  return will_redirect;
+}
+
+bool PrerenderResourceHandler::OnResponseStarted(int request_id,
+                                                 ResourceResponse* response) {
+  if (ShouldPrerender(url_, response)) {
+    BrowserThread::PostTask(
+        BrowserThread::UI,
+        FROM_HERE,
+        NewRunnableMethod(
+            this,
+            &PrerenderResourceHandler::RunCallbackFromUIThread,
+            url_));
+  }
+  return next_handler_->OnResponseStarted(request_id, response);
+}
+
+bool PrerenderResourceHandler::OnWillStart(int request_id,
+                                           const GURL& url,
+                                           bool* defer) {
+  bool will_start = next_handler_->OnWillStart(request_id, url, defer);
+  if (will_start)
+    url_ = url;
+  return will_start;
+}
+
+bool PrerenderResourceHandler::OnWillRead(int request_id,
+                                          net::IOBuffer** buf,
+                                          int* buf_size,
+                                          int min_size) {
+  return next_handler_->OnWillRead(request_id, buf, buf_size, min_size);
+}
+
+bool PrerenderResourceHandler::OnReadCompleted(int request_id,
+                                               int* bytes_read) {
+  return next_handler_->OnReadCompleted(request_id, bytes_read);
+}
+
+bool PrerenderResourceHandler::OnResponseCompleted(
+    int request_id,
+    const URLRequestStatus& status,
+    const std::string& security_info) {
+  return next_handler_->OnResponseCompleted(request_id, status, security_info);
+}
+
+void PrerenderResourceHandler::OnRequestClosed() {
+  next_handler_->OnRequestClosed();
+}
+
+void PrerenderResourceHandler::RunCallbackFromUIThread(const GURL& url) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  prerender_callback_->Run(url);

[darin (slow to review), 2010/12/17 19:58:21]

there seems to be the assumption here that GET requests are idempotent.  that's
not really true in all cases.

ideally, you would inspect the prefetched response to determine if it is
cachable, and then only kick off a prerender if you know that the document is
going to be fetched from the cache.  or maybe you would set some flag to coerce
it to be fetched from the cache (and fail if it cannot be for some reason, as we
do for form resubmissions).

[cbentzel, 2010/12/17 20:03:51]

I can add that to ShouldPrerender - this is called before we decide to
prerender, but after the response headers have been handled [and after
content-sniffing has been done if necessary].

[cbentzel, 2010/12/19 00:40:56]

Now, prerendering only happens if the top-level resource will not need to go
through cache revalidation while the prerendered page could still be used. We
currently will only use prerendered pages 20 seconds after they have been
instantiated.

+}
+
+void PrerenderResourceHandler::StartPrerender(const GURL& url) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  prerender_manager_->AddPreload(url);
+}
+
+// static
+bool PrerenderResourceHandler::CouldPrerender(const net::URLRequest* request) {
+  return ((request->load_flags() & net::LOAD_PREFETCH) &&
+          request->method() == "GET");
+}
+
+// static
+bool PrerenderResourceHandler::ShouldPrerender(

[willchan no longer on Chromium, 2010/12/17 21:45:17]

I'm not sure why this is a private static function rather than put in an
anonymous namespace here.  It doesn't seem to require any access to
PrerenderResourceHandler.

[cbentzel, 2010/12/19 00:40:56]

Gavin had the same concern. I changed it.

+    const GURL& url,
+    const ResourceResponse* response) {
+  return (url.is_valid() &&
+          (url.SchemeIs("http") || url.SchemeIs("https")) &&
+          response->response_head.headers &&
+          response->response_head.headers->response_code() == 200 &&
+          response->response_head.mime_type == "text/html");
+}
+