Add a NavigationThrottle to the public content/ interface

content/browser/loader/navigation_resource_throttle.cc

+// Copyright 2015 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 "content/browser/loader/navigation_resource_throttle.h"
+
+#include "base/callback.h"
+#include "content/browser/frame_host/navigation_handle_impl.h"
+#include "content/browser/frame_host/render_frame_host_impl.h"
+#include "content/public/browser/resource_context.h"
+#include "content/public/browser/resource_controller.h"
+#include "content/public/browser/resource_request_info.h"
+#include "content/public/common/referrer.h"
+#include "net/url_request/redirect_info.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context.h"
+#include "net/url_request/url_request_job_factory.h"
+#include "ui/base/page_transition_types.h"
+
+namespace content {
+
+namespace {
+typedef base::Callback<void(NavigationThrottle::ThrottleCheckResult)>
+    UIChecksPerformedCallback;
+
+void CheckWillStartRequestOnUIThread(UIChecksPerformedCallback callback,
+                                     int render_process_id,
+                                     int render_frame_host_id,
+                                     bool is_post,
+                                     const Referrer& sanitized_referrer,
+                                     bool has_user_gesture,
+                                     ui::PageTransition transition,
+                                     bool is_external_protocol) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  NavigationThrottle::ThrottleCheckResult result = NavigationThrottle::PROCEED;
+  RenderFrameHostImpl* render_frame_host =
+      RenderFrameHostImpl::FromID(render_process_id, render_frame_host_id);
+  if (render_frame_host) {
+    NavigationHandleImpl* navigation_handle =
+        render_frame_host->navigation_handle();
+    if (navigation_handle) {
+      result = navigation_handle->WillStartRequest(is_post, sanitized_referrer,
+                                                   has_user_gesture, transition,
+                                                   is_external_protocol);
+    }
+  }
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(callback, result));
+}
+
+void CheckWillRedirectRequestOnUIThread(UIChecksPerformedCallback callback,
+                                        int render_process_id,
+                                        int render_frame_host_id,
+                                        const GURL& new_url,
+                                        bool new_method_is_post,
+                                        const GURL& new_referrer_url,
+                                        bool new_is_external_protocol) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  NavigationThrottle::ThrottleCheckResult result = NavigationThrottle::PROCEED;
+  RenderFrameHostImpl* render_frame_host =
+      RenderFrameHostImpl::FromID(render_process_id, render_frame_host_id);
+  if (render_frame_host) {
+    NavigationHandleImpl* navigation_handle =
+        render_frame_host->navigation_handle();

[Charlie Reis, 2015/09/18 05:40:02]

Are there races possible here?  Suppose the UI thread has recently replaced the
NavigationHandle with a different one, and a redirect comes in for the old one. 
Is that a problem?

[clamy, 2015/09/18 17:35:39]

Due to all IPCs being processed on the IO thread it is not. The issue could have
come up if we started navigating to a page foo with redirects and then start
navigating to bar. In blink::FrameLoader::StartLoad, a call to stop the
provisional document loader is made
(https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...).
This will result in a ResourceHostMsg_CancelRequest being sent. The
ResourceHostMsg_CancelRequest will cancel the request, leading to this being
deleted. The DidStartProvisionalLoad IPC is sent after in
blink::FrameLoader::StartLoad
(https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...),
therefore it will arrive on the IO thread after the
ResourceHostMsg_CancelRequest has been processed. In particular, any thread hops
made by the NavigationResourceThrottle before its deletion will be processed on
the UI thread before the DidStartProvisionalLoad, so before we create a new
handler for the navigation.

[Charlie Reis, 2015/09/18 17:58:39]

Acknowledged.

+    if (navigation_handle) {
+      RenderProcessHost* rph = RenderProcessHost::FromID(render_process_id);
+      GURL new_validated_url = new_url;
+      rph->FilterURL(false, &new_validated_url);
+      result = navigation_handle->WillRedirectRequest(
+          new_validated_url, new_method_is_post, new_referrer_url,
+          new_is_external_protocol);
+    }
+  }
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                          base::Bind(callback, result));
+}
+}  // namespace
+
+NavigationResourceThrottle::NavigationResourceThrottle(net::URLRequest* request)
+    : request_(request), weak_ptr_factory_(this) {}
+
+NavigationResourceThrottle::~NavigationResourceThrottle() {}
+
+void NavigationResourceThrottle::WillStartRequest(bool* defer) {
+  const ResourceRequestInfo* info = ResourceRequestInfo::ForRequest(request_);
+  if (!info)
+    return;
+
+  int render_process_id, render_frame_id;
+  if (!info->GetAssociatedRenderFrame(&render_process_id, &render_frame_id))
+    return;
+
+  bool is_external_protocol =
+      !info->GetContext()->GetRequestContext()->job_factory()->IsHandledURL(
+          request_->url());
+  UIChecksPerformedCallback callback =
+      base::Bind(&NavigationResourceThrottle::OnUIChecksPerformed,
+                 weak_ptr_factory_.GetWeakPtr());
+  DCHECK(request_->method() == "POST" || request_->method() == "GET");
+  BrowserThread::PostTask(

[Charlie Reis, 2015/09/18 05:40:02]

Sanity check: This is doing a hop to the UI thread for every navigation, right? 
Are there performance concerns about this, and do we need to prevent other code
from making repeated hops?  For example, CrossSiteResourceHandler hops to the UI
thread for policy checks in --site-per-process.  Seems like we should avoid
doing repeated hops.

[clamy, 2015/09/18 17:35:39]

On Android we are replacing a ResourceThrottle that made thread hops n every
request, so this is similar performance wise. This is not the case on desktop,
but I think thread hops are less of an issue in that case. The goal in the end
is to remove all ResourceThrottles for navigations, which would ensure that only
one thread hop is ever made for all navigations. For the
CrossSiteResourceHandler, depending on when PlzNavigate and OOPIF ship, we could
rewrite it as a NavigationThrottle, meaning we only also do one thread hop
there.

[nasko, 2015/09/18 17:58:19]

I don't think we can ensure only one thread hop per navigation. Each of the
events (will send request, will redirect, ...) will require a separate hop on
its own. I do agree that for each event, only one thread hop must be made, but
we can't avoid multiple hops per navigation if we want to support the full
NavigationHandle API.

[Charlie Reis, 2015/09/18 17:58:39]

Acknowledged.

[clamy, 2015/09/18 18:21:23]

Yes that's what I meant (but my wording was not good :).

+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&CheckWillStartRequestOnUIThread, callback, render_process_id,
+                 render_frame_id, request_->method() == "POST",
+                 Referrer::SanitizeForRequest(
+                     request_->url(), Referrer(GURL(request_->referrer()),
+                                               info->GetReferrerPolicy())),
+                 info->HasUserGesture(), info->GetPageTransition(),
+                 is_external_protocol));
+  *defer = true;
+}
+
+void NavigationResourceThrottle::WillRedirectRequest(
+    const net::RedirectInfo& redirect_info,
+    bool* defer) {
+  const ResourceRequestInfo* info = ResourceRequestInfo::ForRequest(request_);
+  if (!info)
+    return;
+
+  int render_process_id, render_frame_id;
+  if (!info->GetAssociatedRenderFrame(&render_process_id, &render_frame_id))
+    return;
+
+  bool new_is_external_protocol =
+      !info->GetContext()->GetRequestContext()->job_factory()->IsHandledURL(
+          request_->url());
+  DCHECK(redirect_info.new_method == "POST" ||
+         redirect_info.new_method == "GET");
+  UIChecksPerformedCallback callback =
+      base::Bind(&NavigationResourceThrottle::OnUIChecksPerformed,
+                 weak_ptr_factory_.GetWeakPtr());
+  BrowserThread::PostTask(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&CheckWillRedirectRequestOnUIThread, callback,
+                 render_process_id, render_frame_id, redirect_info.new_url,
+                 redirect_info.new_method == "POST",
+                 GURL(redirect_info.new_referrer), new_is_external_protocol));
+  *defer = true;
+}
+
+const char* NavigationResourceThrottle::GetNameForLogging() const {
+  return "NavigationResourceThrottle";
+}
+
+void NavigationResourceThrottle::OnUIChecksPerformed(
+    NavigationThrottle::ThrottleCheckResult result) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (result == NavigationThrottle::CANCEL_AND_IGNORE) {
+    controller()->CancelAndIgnore();
+  } else {
+    controller()->Resume();
+  }
+}
+
+}  // namespace content