Fix RenderThreadImplBrowserTest by adding ScopedIPCSupport

Removed 2 tests from the filter:
-RenderThreadImplBrowserTest.NonResourceDispatchIPCTasksDontGoThroughScheduler
  * Fixed by adding |ScopedIPCSupport| after |InitializeMojo()|.
-RenderThreadImplBrowserTest.ResourceDispatchIPCTasksGoThroughScheduler
  * This test no longer exists.

-- Note: the first test used to crash with log:
[91028:91028:0307/112240.705814:2593896751430:FATAL:scoped_refptr.h(219)] Check failed: ptr_.
#0 0x7f69ce3986ad base::debug::StackTrace::StackTrace()
#1 0x7f69ce396b9c base::debug::StackTrace::StackTrace()
#2 0x7f69ce41ebca logging::LogMessage::~LogMessage()
#3 0x7f69d0131b42 scoped_refptr<>::operator->()
#4 0x7f69d016d49b mojo::edk::NodeController::SendBrokerClientInvitation()
#5 0x7f69d013becf mojo::edk::Core::SendBrokerClientInvitation()
#6 0x7f69d01c06ea mojo::edk::OutgoingBrokerClientInvitation::Send()
#7 0x7f69c9cb0df8 content::internal::ChildProcessLauncherHelper::PostLaunchOnLauncherThread()
#8 0x7f69c9cb08cd content::internal::ChildProcessLauncherHelper::LaunchOnLauncherThread()


Bug: 729848
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: I18d85b91b5db78087c7e507df3d38da767327e1b
Reviewed-on: https://chromium-review.googlesource.com/953248Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Chong Zhang <chongz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541638}

content/renderer/render_thread_impl_browsertest.cc

@@ -47,6 +47,7 @@
 #include "ipc/ipc_channel_mojo.h"
 #include "mojo/edk/embedder/embedder.h"
 #include "mojo/edk/embedder/outgoing_broker_client_invitation.h"
+#include "mojo/edk/embedder/scoped_ipc_support.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/WebKit/public/platform/scheduler/renderer/renderer_scheduler.h"
 #include "third_party/WebKit/public/platform/scheduler/test/renderer_scheduler_test_support.h"
@@ -177,6 +178,8 @@ class RenderThreadImplBrowserTest : public testing::Test {
         blink::scheduler::GetSingleThreadTaskRunnerForTesting();
 
     InitializeMojo();
+    mojo_ipc_support_.reset(new mojo::edk::ScopedIPCSupport(
+        io_task_runner, mojo::edk::ScopedIPCSupport::ShutdownPolicy::FAST));
     shell_context_.reset(new TestServiceManagerContext);
     mojo::edk::OutgoingBrokerClientInvitation invitation;
     service_manager::Identity child_identity(
@@ -254,6 +257,7 @@ class RenderThreadImplBrowserTest : public testing::Test {
   std::unique_ptr<TestServiceManagerContext> shell_context_;
   std::unique_ptr<ChildConnection> child_connection_;
   std::unique_ptr<IPC::ChannelProxy> channel_;
+  std::unique_ptr<mojo::edk::ScopedIPCSupport> mojo_ipc_support_;
 
   std::unique_ptr<MockRenderProcess> mock_process_;
   scoped_refptr<QuitOnTestMsgFilter> test_msg_filter_;

testing/buildbot/filters/mojo.fyi.network_content_browsertests.filter

@@ -56,8 +56,6 @@
 -PreviewsStateResourceDispatcherHostBrowserTest.ShouldEnableLoFiModeOn
 -PreviewsStateResourceDispatcherHostBrowserTest.ShouldEnableLoFiModeReload
 -PreviewsStateResourceDispatcherHostBrowserTest.ShouldEnableLoFiModeReloadDisableLoFi
--RenderThreadImplBrowserTest.NonResourceDispatchIPCTasksDontGoThroughScheduler
--RenderThreadImplBrowserTest.ResourceDispatchIPCTasksGoThroughScheduler
 -RenderViewBrowserTest.ConfirmCacheInformationPlumbed
 -RequestDataResourceDispatcherHostBrowserTest.Basic
 -RequestDataResourceDispatcherHostBrowserTest.BasicCrossSite