Enable spare RenderProcessHost to be preinitialized.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index ff0b0817849d0b10a56dd97a8010bd2618ecd666..79eae89a259b468c77e0d3f935e9429167348bf8 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -3155,6 +3155,12 @@ const FeatureEntry kFeatureEntries[] = {
      flag_descriptions::kResourceLoadSchedulerDescription, kOsAll,
      FEATURE_VALUE_TYPE(features::kResourceLoadScheduler)},
 
+#if defined(OS_ANDROID)
+    {"omnibox-spare-renderer", flag_descriptions::kOmniboxSpareRendererName,
+     flag_descriptions::kOmniboxSpareRendererDescription, kOsAndroid,
+     FEATURE_VALUE_TYPE(chrome::android::kOmniboxSpareRenderer)},
+#endif
+
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms/enums.xml. See note in
     // enums.xml and don't forget to run AboutFlagsHistogramTest unit test.