Use StopChildProcess instead of base::KillProcess to kill a renderer process

content/public/test/mock_render_process_host.cc

Index: content/public/test/mock_render_process_host.cc
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index d98f6e83c2c5dc3e7799260a577827ccbfd90c76..008b1dc82f8d895a87f9d9997d457981740713d5 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -114,6 +114,10 @@ bool MockRenderProcessHost::FastShutdownIfPossible() {
   return true;
 }
 
+bool MockRenderProcessHost::FastShutdown(int exit_code, bool wait) {
+  return true;
+}
+
 bool MockRenderProcessHost::FastShutdownStarted() const {
   return fast_shutdown_started_;
 }