Move existing kSitePerProcess checks to a policy-oracle object

content/browser/loader/cross_site_resource_handler.cc

Index: content/browser/loader/cross_site_resource_handler.cc
diff --git a/content/browser/loader/cross_site_resource_handler.cc b/content/browser/loader/cross_site_resource_handler.cc
index ebf40eb023a6abfd0047b64e11de9ef04dd57eb7..d68fb9b7dd5378b7f4d4eef351be5ac09251230f 100644
--- a/content/browser/loader/cross_site_resource_handler.cc
+++ b/content/browser/loader/cross_site_resource_handler.cc
@@ -16,6 +16,7 @@
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 #include "content/browser/loader/resource_request_info_impl.h"
 #include "content/browser/site_instance_impl.h"
+#include "content/common/site_isolation_policy.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/global_request_id.h"
@@ -71,8 +72,7 @@ void OnCrossSiteResponseHelper(const CrossSiteResponseParams& params) {
       // We should only swap processes for subframes in --site-per-process mode.
       // CrossSiteResourceHandler is not installed on subframe requests in
       // default Chrome.
-      CHECK(base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kSitePerProcess));
+      CHECK(SiteIsolationPolicy::AreCrossProcessFramesPossible());
     }
     rfh->OnCrossSiteResponse(
         params.global_request_id, cross_site_transferring_request.Pass(),
@@ -87,8 +87,7 @@ void OnCrossSiteResponseHelper(const CrossSiteResponseParams& params) {
 
 // Returns whether a transfer is needed by doing a check on the UI thread.
 bool CheckNavigationPolicyOnUI(GURL url, int process_id, int render_frame_id) {
-  CHECK(base::CommandLine::ForCurrentProcess()->HasSwitch(
-      switches::kSitePerProcess));
+  CHECK(SiteIsolationPolicy::AreCrossProcessFramesPossible());
   RenderFrameHostImpl* rfh =
       RenderFrameHostImpl::FromID(process_id, render_frame_id);
   if (!rfh)
@@ -99,12 +98,18 @@ bool CheckNavigationPolicyOnUI(GURL url, int process_id, int render_frame_id) {
   if (!rfh->GetSiteInstance()->HasSite())
     return false;
 
-  // TODO(nasko): This check is very simplistic and is used temporarily only
-  // for --site-per-process. It should be updated to match the check performed
-  // by RenderFrameHostManager::UpdateStateForNavigate.
-  return !SiteInstance::IsSameWebSite(
-      rfh->GetSiteInstance()->GetBrowserContext(),
-      rfh->GetSiteInstance()->GetSiteURL(), url);
+  // TODO(nasko, nick): These following --site-per-process checks are
+  // overly simplistic. Update them to match all the cases
+  // considered by RenderFrameHostManager::DetermineSiteInstanceForURL.
+  if (SiteInstance::IsSameWebSite(rfh->GetSiteInstance()->GetBrowserContext(),
+                                  rfh->GetSiteInstance()->GetSiteURL(), url)) {
+    return false;  // The same site, no transition needed.
+  }
+
+  // The sites differ. If either one requires a dedicated process,
+  // then a transfer is needed.
+  return rfh->GetSiteInstance()->RequiresDedicatedProcess() ||
+         SiteIsolationPolicy::DoesSiteRequireDedicatedProcess(url);
 }
 
 }  // namespace
@@ -159,12 +164,12 @@ bool CrossSiteResourceHandler::OnNormalResponseStarted(
 
   ResourceRequestInfoImpl* info = GetRequestInfo();
 
-  // We only need to pause the response if a transfer to a different process is
-  // required.  Other cross-process navigations can proceed immediately, since
-  // we run the unload handler at commit time.
-  // Note that a process swap may no longer be necessary if we transferred back
-  // into the original process due to a redirect.
-  bool should_transfer =
+  // The content embedder can decide that a transfer to a different process is
+  // required for this URL.  If so, pause the response now.  Other cross process
+  // navigations can proceed immediately, since we run the unload handler at
+  // commit time.  Note that a process swap may no longer be necessary if we
+  // transferred back into the original process due to a redirect.
+  bool definitely_transfer =
       GetContentClient()->browser()->ShouldSwapProcessesForRedirect(
           info->GetContext(), request()->original_url(), request()->url());
 
@@ -189,30 +194,33 @@ bool CrossSiteResourceHandler::OnNormalResponseStarted(
     return next_handler_->OnResponseStarted(response, defer);
   }
 
-  // When the --site-per-process flag is passed, we transfer processes for
-  // cross-site navigations. This is skipped if a transfer is already required
-  // or for WebUI processes for now, since pages like the NTP host multiple
-  // cross-site WebUI iframes.
-  if (!should_transfer &&
-      base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kSitePerProcess) &&
+  if (definitely_transfer) {
+    // Now that we know a transfer is needed and we have something to commit, we
+    // pause to let the UI thread set up the transfer.
+    StartCrossSiteTransition(response);
+
+    // Defer loading until after the new renderer process has issued a
+    // corresponding request.
+    *defer = true;
+    OnDidDefer();
+    return true;
+  }
+
+  // In the site-per-process model, we may also decide (independently from the
+  // content embedder's ShouldSwapProcessesForRedirect decision above) that a
+  // process transfer is needed.  For that we need to consult the navigation
+  // policy on the UI thread, so pause the response.  Process transfers are
+  // skipped for WebUI processes for now, since e.g. chrome://settings has
+  // multiple "cross-site" chrome:// frames, and that doesn't yet work cross-
+  // process.
+  if (SiteIsolationPolicy::AreCrossProcessFramesPossible() &&
       !ChildProcessSecurityPolicyImpl::GetInstance()->HasWebUIBindings(
           info->GetChildID())) {
     return DeferForNavigationPolicyCheck(info, response, defer);
   }
 
-  if (!should_transfer)
-    return next_handler_->OnResponseStarted(response, defer);
-
-  // Now that we know a transfer is needed and we have something to commit, we
-  // pause to let the UI thread set up the transfer.
-  StartCrossSiteTransition(response);
-
-  // Defer loading until after the new renderer process has issued a
-  // corresponding request.
-  *defer = true;
-  OnDidDefer();
-  return true;
+  // No deferral needed. Pass the response through.
+  return next_handler_->OnResponseStarted(response, defer);
 }
 
 void CrossSiteResourceHandler::ResumeOrTransfer(bool is_transfer) {