Revert the fix for 538784.

Revert the fix for 538784 and disable its test.

I'll re-land this after fixing up unittests that inadvertently
depended on the unsafe behavior.

BUG=538784
TBR=nasko@chromium.org

Committed: https://crrev.com/f3b22237bceb64cc0a3be9ecbdc2d7da83ef6e54
Cr-Commit-Position: refs/heads/master@{#352943}

[ncarter (slow), 2015-10-07 18:03:22]

nick@chromium.org changed reviewers:
+ nasko@chromium.org

[ncarter (slow), 2015-10-07 18:03:50]

The CQ bit was checked by nick@chromium.org

[ncarter (slow), 2015-10-07 18:04:19]

TBRing since this is turning the site isolation bot red currently.

[commit-bot: I haz the power, 2015-10-07 18:09:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1398473002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1398473002/1

[commit-bot: I haz the power, 2015-10-07 19:25:02]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-07 19:25:04]

Failed to apply patch for content/browser/loader/cross_site_resource_handler.cc:
While running git apply --index -3 -p1;
  error: patch failed: content/browser/loader/cross_site_resource_handler.cc:96
  error: repository lacks the necessary blob to fall back on 3-way merge.
  error: content/browser/loader/cross_site_resource_handler.cc: patch does not
apply

Patch:       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
47c5390f9672fcb57d14e6d3d47fcc0634154a37..4539735733a149c27124d14ce2d0e71f5f4d57ae
100644
--- a/content/browser/loader/cross_site_resource_handler.cc
+++ b/content/browser/loader/cross_site_resource_handler.cc
@@ -96,10 +96,10 @@ CheckNavigationPolicyOnUI(GURL real_url, int process_id, int
render_frame_id) {
   // Without a valid RFH against which to check, we must cancel the request,
   // to prevent the resource at |url| from being delivered to a potentially
   // unsuitable renderer process.
-  if (!rfh) {
-    CHECK(false);
-    return CrossSiteResourceHandler::NavigationDecision::CANCEL_REQUEST;
-  }
+  // TODO(nick): Switch this back to NavigationDecision::CANCEL once we fix
+  // existing transfer unittests that don't specify a valid rfh ID.
+  if (!rfh)
+    return CrossSiteResourceHandler::NavigationDecision::USE_EXISTING_RENDERER;
 
   RenderFrameHostManager* manager = rfh->frame_tree_node()->render_manager();
   if (manager->IsRendererTransferNeededForNavigation(rfh, real_url))

[commit-bot: I haz the power, 2015-10-07 19:28:46]

The CQ bit was unchecked by commit-bot@chromium.org

[ncarter (slow), 2015-10-07 20:10:10]

The CQ bit was checked by nick@chromium.org

[commit-bot: I haz the power, 2015-10-07 20:10:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1398473002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1398473002/20001

[commit-bot: I haz the power, 2015-10-07 21:05:09]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-07 21:05:46]

Patchset 2 (id:??) landed as
https://crrev.com/f3b22237bceb64cc0a3be9ecbdc2d7da83ef6e54
Cr-Commit-Position: refs/heads/master@{#352943}