Revert "Enable NavigationRacesWithSitelessCommitInDefaultProcess on all platforms."

This reverts commit 0b97d41c.

Reason for revert: The failures were reproduced... in many places. Hopefully enough data to help debug.
Bug: 1143207

Original change's description:
> Enable NavigationRacesWithSitelessCommitInDefaultProcess on all platforms.
>
> Unable to reproduce flakiness locally. Enabling tests and removing skip
> test logic for --site-per-process. Code was added to remove this flag in
> SetUpCommandLine() so the tests can run on all platforms.
>
> Bug: 1110497
> Change-Id: I552f82d1fe4786e59cd624edf5504b713318d523
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2500280
> Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
> Commit-Queue: Aaron Colwell <acolwell@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#821477}

TBR=acolwell@chromium.org,alexmos@chromium.org

Change-Id: I0d6472a0b2424b65db61559fb330275463fca9c8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1110497
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2504266Reviewed-by: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Commit-Queue: Michael van Ouwerkerk <mvanouwerkerk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821671}

content/browser/renderer_host/render_frame_host_manager_browsertest.cc

@@ -8744,7 +8744,6 @@ class RenderFrameHostManagerDefaultProcessTest
   void SetUpCommandLine(base::CommandLine* command_line) override {
     RenderFrameHostManagerTest::SetUpCommandLine(command_line);
     command_line->AppendSwitch(switches::kDisableSiteIsolation);
-    command_line->RemoveSwitch(switches::kSitePerProcess);
 
     if (AreAllSitesIsolatedForTesting()) {
       LOG(WARNING) << "This test should be run without strict site isolation. "
@@ -8758,6 +8757,14 @@ class RenderFrameHostManagerDefaultProcessTest
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostManagerDefaultProcessTest);
 };
 
+// TODO(crbug.com/1110497): flaky on Android builders since 2020-07-28.
+#if defined(OS_ANDROID)
+#define MAYBE_NavigationRacesWithSitelessCommitInDefaultProcess \
+  DISABLED_NavigationRacesWithSitelessCommitInDefaultProcess
+#else
+#define MAYBE_NavigationRacesWithSitelessCommitInDefaultProcess \
+  NavigationRacesWithSitelessCommitInDefaultProcess
+#endif
 // Ensure that the default process can be used for URLs that don't assign a site
 // to the SiteInstance, when Site Isolation is not enabled.
 // 1. Visit foo.com.
@@ -8767,8 +8774,13 @@ class RenderFrameHostManagerDefaultProcessTest
 // https://crbug.com/838348.)
 // All navigations should use the default process, and we should not crash.
 // See https://crbug.com/977956.
-IN_PROC_BROWSER_TEST_P(RenderFrameHostManagerDefaultProcessTest,
-                       NavigationRacesWithSitelessCommitInDefaultProcess) {
+IN_PROC_BROWSER_TEST_P(
+    RenderFrameHostManagerDefaultProcessTest,
+    MAYBE_NavigationRacesWithSitelessCommitInDefaultProcess) {
+  // This test is designed to run without strict site isolation.
+  if (AreAllSitesIsolatedForTesting())
+    return;
+
   ASSERT_TRUE(embedded_test_server()->Start());
   WebContentsImpl* web_contents =
       static_cast<WebContentsImpl*>(shell()->web_contents());