Replace --ppapi-keep-alive-throttle command line switch with IPC parameter.

ppapi/shared_impl/ppapi_switches.cc

Index: ppapi/shared_impl/ppapi_switches.cc
diff --git a/ppapi/shared_impl/ppapi_switches.cc b/ppapi/shared_impl/ppapi_switches.cc
index 2a3f1c286008740104d5aaa8df81d6bf93205f95..84ba25034ecb4a361bf4531119be68d440b14959 100644
--- a/ppapi/shared_impl/ppapi_switches.cc
+++ b/ppapi/shared_impl/ppapi_switches.cc
@@ -9,7 +9,4 @@ namespace switches {
 // Enables the testing interface for PPAPI.
 const char kEnablePepperTesting[] = "enable-pepper-testing";
 
-// Specifies throttling time in milliseconds for PpapiHostMsg_Keepalive IPCs.
-const char kPpapiKeepAliveThrottle[] = "ppapi-keep-alive-throttle";
-
 }  // namespace switches