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

content/public/test/mock_render_process_host.h

Index: content/public/test/mock_render_process_host.h
diff --git a/content/public/test/mock_render_process_host.h b/content/public/test/mock_render_process_host.h
index 81df68607d630ff83f0475bb9b2284ba3078724f..4e2cf8e9595a7a209f8a5a046ea8c676e0d36623 100644
--- a/content/public/test/mock_render_process_host.h
+++ b/content/public/test/mock_render_process_host.h
@@ -47,6 +47,7 @@ class MockRenderProcessHost : public RenderProcessHost {
   bool IsIsolatedGuest() const override;
   StoragePartition* GetStoragePartition() const override;
   virtual void AddWord(const base::string16& word);
+  bool Shutdown(int exit_code, bool wait) override;
   bool FastShutdownIfPossible() override;
   bool FastShutdownStarted() const override;
   void DumpHandles() override;