Adding Navigation Throttles to DevTools

content/browser/frame_host/navigation_handle_impl.cc

Index: content/browser/frame_host/navigation_handle_impl.cc
diff --git a/content/browser/frame_host/navigation_handle_impl.cc b/content/browser/frame_host/navigation_handle_impl.cc
index d7dcbefabbf2f06121040f756c61a2c45587d524..75362728f5a869d53ac1146337e0c7527fe6d85b 100644
--- a/content/browser/frame_host/navigation_handle_impl.cc
+++ b/content/browser/frame_host/navigation_handle_impl.cc
@@ -7,6 +7,7 @@
 #include <utility>
 
 #include "base/logging.h"
+#include "content/browser/devtools/render_frame_devtools_agent_host.h"
 #include "content/browser/frame_host/frame_tree_node.h"
 #include "content/browser/frame_host/navigator.h"
 #include "content/browser/frame_host/navigator_delegate.h"
@@ -323,6 +324,17 @@ void NavigationHandleImpl::WillStartRequest(
   state_ = WILL_SEND_REQUEST;
   complete_callback_ = callback;
 
+  RegisterNavigationThrottles();
+
+  // Notify each throttle of the request.
+  NavigationThrottle::ThrottleCheckResult result = CheckWillStartRequest();
+
+  // If the navigation is not deferred, run the callback.
+  if (result != NavigationThrottle::DEFER)
+    RunCompleteCallback(result);
+}
+
+void NavigationHandleImpl::RegisterNavigationThrottles() {

[clamy, 2016/07/11 14:20:36]

Please ensure that the order of the functions in the .cc file matches the one in
the .h file.

[alex clarke (OOO till 29th), 2016/07/11 21:21:12]

Done.

   // Register the navigation throttles. The ScopedVector returned by
   // GetNavigationThrottles is not assigned to throttles_ directly because it
   // would overwrite any throttle previously added with
@@ -334,13 +346,10 @@ void NavigationHandleImpl::WillStartRequest(
                       throttles_to_register.end());
     throttles_to_register.weak_clear();
   }
-
-  // Notify each throttle of the request.
-  NavigationThrottle::ThrottleCheckResult result = CheckWillStartRequest();
-
-  // If the navigation is not deferred, run the callback.
-  if (result != NavigationThrottle::DEFER)
-    RunCompleteCallback(result);
+  std::unique_ptr<NavigationThrottle> devtools_throttle =

[clamy, 2016/07/11 14:20:36]

Sanity check: this will mean that the devtools throttle will execute last. In
particular, if any other throttle cancel the navigation it won't know about it.
Is this WAI?

[alex clarke (OOO till 29th), 2016/07/11 21:21:12]

That is what I intended.  My thoughts where we'd want to know about navigations
that are /actually/ going to occur rather than ones that get cancelled by some
other filter.

+      RenderFrameDevToolsAgentHost::GetThrottleForNavigation(this);
+  if (devtools_throttle)
+    throttles_.push_back(devtools_throttle.release());
 }
 
 void NavigationHandleImpl::WillRedirectRequest(