Enable spare RenderProcessHost to be preinitialized.

content/browser/renderer_host/render_process_host_browsertest.cc

Index: content/browser/renderer_host/render_process_host_browsertest.cc
diff --git a/content/browser/renderer_host/render_process_host_browsertest.cc b/content/browser/renderer_host/render_process_host_browsertest.cc
index 866e829d1b74c93dad22fc5b77ee71e84cf19598..3ed02d00cb5dc4c676cc1c43e7641dfe10c5dce4 100644
--- a/content/browser/renderer_host/render_process_host_browsertest.cc
+++ b/content/browser/renderer_host/render_process_host_browsertest.cc
@@ -17,6 +17,9 @@
 #include "content/public/test/content_browser_test_utils.h"
 #include "content/public/test/test_service.mojom.h"
 #include "content/shell/browser/shell.h"
+#include "content/shell/browser/shell_browser_context.h"
+#include "content/shell/browser/shell_browser_main_parts.h"
+#include "content/shell/browser/shell_content_browser_client.h"
 #include "media/base/bind_to_current_loop.h"
 #include "media/base/media_switches.h"
 #include "media/base/test_data_util.h"
@@ -126,10 +129,77 @@ IN_PROC_BROWSER_TEST_F(RenderProcessHostTest,
   another_url = another_url.ReplaceComponents(replace_host);
   NavigateToURL(CreateBrowser(), another_url);
 
-  // Expect that we got another process (the guest renderer was not reused).
+  // Expect that we got another process (the guest RenderProcessHost was not
+  // reused).
   EXPECT_EQ(2, RenderProcessHostCount());
 }
 
+IN_PROC_BROWSER_TEST_F(RenderProcessHostTest, SpareRenderProcessHostTaken) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  RenderProcessHost::WarmupSpareRenderProcessHost(
+      ShellContentBrowserClient::Get()->browser_context());
+  RenderProcessHost* spare_renderer =
+      RenderProcessHostImpl::GetSpareRenderProcessHostForTesting();
+  EXPECT_NE(nullptr, spare_renderer);
+
+  GURL test_url = embedded_test_server()->GetURL("/simple_page.html");
+  Shell* window = CreateBrowser();
+  NavigateToURL(window, test_url);
+
+  EXPECT_EQ(spare_renderer,
+            window->web_contents()->GetMainFrame()->GetProcess());
+
+  // The spare render process host should no longer be available.
+  EXPECT_EQ(nullptr,
+            RenderProcessHostImpl::GetSpareRenderProcessHostForTesting());
+}
+
+IN_PROC_BROWSER_TEST_F(RenderProcessHostTest, SpareRenderProcessHostNotTaken) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  RenderProcessHost::WarmupSpareRenderProcessHost(
+      ShellContentBrowserClient::Get()->off_the_record_browser_context());
+  RenderProcessHost* spare_renderer =
+      RenderProcessHostImpl::GetSpareRenderProcessHostForTesting();
+  GURL test_url = embedded_test_server()->GetURL("/simple_page.html");
+  Shell* window = CreateBrowser();
+  NavigateToURL(window, test_url);
+
+  // There should have been another process created for the navigation.
+  EXPECT_NE(spare_renderer,
+            window->web_contents()->GetMainFrame()->GetProcess());
+
+  // The spare RenderProcessHost should have been cleaned up. Note this
+  // behavior is identical to what would have happened if the RenderProcessHost
+  // were taken.
+  EXPECT_EQ(nullptr,
+            RenderProcessHostImpl::GetSpareRenderProcessHostForTesting());
+}
+
+IN_PROC_BROWSER_TEST_F(RenderProcessHostTest, SpareRenderProcessHostKilled) {
+  RenderProcessHost::WarmupSpareRenderProcessHost(
+      ShellContentBrowserClient::Get()->browser_context());
+
+  RenderProcessHost* spare_renderer =
+      RenderProcessHostImpl::GetSpareRenderProcessHostForTesting();
+  mojom::TestServicePtr service;
+  ASSERT_NE(nullptr, spare_renderer);
+  BindInterface(spare_renderer, &service);
+
+  base::RunLoop run_loop;
+  set_process_exit_callback(run_loop.QuitClosure());
+  spare_renderer->AddObserver(this);  // For process_exit_callback.
+
+  // Should reply with a bad message and cause process death.
+  service->DoSomething(base::Bind(&base::DoNothing));
+  run_loop.Run();
+
+  // The spare RenderProcessHost should disappear when its process dies.
+  EXPECT_EQ(nullptr,
+            RenderProcessHostImpl::GetSpareRenderProcessHostForTesting());
+}
+
 class ShellCloser : public RenderProcessHostObserver {
  public:
   ShellCloser(Shell* shell, std::string* logging_string)