Move existing kSitePerProcess checks to a policy-oracle object

content/public/test/browser_test_utils.h

Index: content/public/test/browser_test_utils.h
diff --git a/content/public/test/browser_test_utils.h b/content/public/test/browser_test_utils.h
index bd5cddcb53ad8cda7a4a9b02575e9de483c0bb9c..812cb35ad9b8f85291e3e9ebd80b4f153d08978f 100644
--- a/content/public/test/browser_test_utils.h
+++ b/content/public/test/browser_test_utils.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/callback.h"
+#include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/ref_counted.h"
@@ -246,6 +247,19 @@ void WaitForInterstitialDetach(content::WebContents* web_contents);
 void RunTaskAndWaitForInterstitialDetach(content::WebContents* web_contents,
                                          const base::Closure& task);
 
+// Returns true if all sites are isolated. Typically used to bail from a test
+// that is incompatible with --site-per-process.
+bool AreAllSitesIsolatedForTesting();
+
+// Appends --site-per-process to the command line, enabling tests to exercise
+// site isolation and cross-process iframes.
+//
+// TODO(nick): In some places this method is called from the top of a test
+// body. That's not strictly safe (it's setting a command line after it
+// already may have been read). We should try make that pattern safer, as it
+// makes browser tests easier to write.
+void IsolateAllSitesForTesting(base::CommandLine* command_line);
+
 // Waits until all resources have loaded in the given RenderFrameHost.
 // When the load completes, this function sends a "pageLoadComplete" message
 // via domAutomationController. The caller should make sure this extra