Introduce support for origins that require process isolation.

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 1704d64df5d47419201301960b7af5103d74e13d..3238ea6f711fb3f7535f90e295a5cfd7e0707b40 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -604,6 +604,11 @@ const char kInProcessGPU[]                  = "in-process-gpu";
 // connection from the browser before killing itself.
 const char kIPCConnectionTimeout[]          = "ipc-connection-timeout";
 
+// Enable process isolation for a set of origins, specified as a
+// comma-separated list. For example:
+//   --isolate-origins=https://www.foo.com,https://www.bar.com
+const char kIsolateOrigins[] = "isolate-origins";
+
 // Chrome is running in Mash.
 const char kIsRunningInMash[] = "is-running-in-mash";