Disable ProactivelySwapBrowsingInstancesCrossSiteReuseProcessTests when all sites are isolated

These tests asserts that a cross-site navigation will not result in
process-reuse in some circumstances. This will always be true when all
sites are isolated, so we can skip the test when that's the case. Note
that other ProactivelySwapBrowsingInstancesCrossSiteReuseProcessTests
already does this (skip when all sites are isolated).

Bug: 1136303
Change-Id: I7e08319035feea3d0ab2c1ee4e5c1d609401bbcc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462994Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816436}

content/browser/renderer_host/render_frame_host_manager_browsertest.cc

@@ -5935,6 +5935,8 @@ IN_PROC_BROWSER_TEST_P(
 IN_PROC_BROWSER_TEST_P(
     ProactivelySwapBrowsingInstancesCrossSiteReuseProcessTest,
     NavigationToSiteThatRequiresDedicatedProcess) {
+  if (AreAllSitesIsolatedForTesting())
+    return;
   ASSERT_TRUE(embedded_test_server()->Start());
   GURL a_url(embedded_test_server()->GetURL("a.com", "/title1.html"));
   GURL b_url(embedded_test_server()->GetURL("b.com", "/title1.html"));
@@ -5971,6 +5973,8 @@ IN_PROC_BROWSER_TEST_P(
 IN_PROC_BROWSER_TEST_P(
     ProactivelySwapBrowsingInstancesCrossSiteReuseProcessTest,
     NavigationFromSiteThatRequiresDedicatedProcess) {
+  if (AreAllSitesIsolatedForTesting())
+    return;
   ASSERT_TRUE(embedded_test_server()->Start());
   GURL a_url(embedded_test_server()->GetURL("a.com", "/title1.html"));
   GURL b_url(embedded_test_server()->GetURL("b.com", "/title1.html"));