Drop CreateChildFrame messages when swapping out.

Drop CreateChildFrame messages when swapping out.

There is a race condition in the current state of the code where in cross-process navigation we swap the existing RenderFrameHost with a new RenderFrameHost. If the existing host sends an IPC message to create a new child frame, it arrives on the IO thread, allocates a routing id based of the existing process (p1) and does a PostTask to the UI thread. If there is a CommitPending event either executing on the UI thread or in the task queue before the task posted from the IO thread, it will end up putting the existing RenderFrameHost in swapped out state (or waiting for swapped out). When the task to create a child frame is executed after that, it creates a new RenderFrameHost, but it uses the "current" process (p2), which is different than the process that sent the message (p1). This manifests sometimes as adding duplicate routing ids to RenderProcessHost and is in general really bad bug.

BUG=415059, 423691, 381990
Review URL: https://codereview.chromium.org/642813007

Cr-Commit-Position: refs/heads/master@{#299939}
(cherry picked from commit dcdb02fab210ec5f7b8b560075ce96d0f48f344c)

Conflicts:
	content/browser/frame_host/navigator_impl_unittest.cc

R=creis@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/a6a21983b1a29ad11d30782c66d95facca65ab55

[nasko, 2014-10-20 17:38:54]

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

[nasko, 2014-10-20 17:38:55]

Hey Charlie,
This is a merge of the duplicate routing ID fix into M39 branch. Since
content/browser/frame_host/navigator_impl_unittest.cc was added just a couple of
weeks ago, I'm dropping it from the merge. It only changed because of method
signature change, so there should be no loss in test coverage.
Thanks!
Nasko

[Charlie Reis, 2014-10-20 18:26:47]

LGTM

[nasko, 2014-10-20 18:32:24]

Committed patchset #1 (id:1) manually as
a6a21983b1a29ad11d30782c66d95facca65ab55 (presubmit successful).

[nasko, 2014-10-20 21:00:57]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/663183003/ by nasko@chromium.org.

The reason for reverting is: It broke compile since this CL relies on
https://crrev.com/cce56cd951f6685a0120db63418aa7e6d3df28f2 and it isn't in this
branch..