Use valid /prefetch arguments for process launches on Windows. - do not submit

components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc

Index: components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc
diff --git a/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc b/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc
index 6aa82a19d93e59d8da9f80ca767206fe5f438be6..522481030252f736b939a9f055a47e126e312488 100644
--- a/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc
+++ b/components/startup_metric_utils/common/pre_read_field_trial_utils_win.cc
@@ -31,6 +31,7 @@ const base::char16 kHighPriorityVariationName[] = L"HighPriority";
 const base::char16 kOnlyIfColdVariationName[] = L"OnlyIfCold";
 const base::char16 kPrefetchVirtualMemoryVariationName[] =
     L"PrefetchVirtualMemory";
+const base::char16 kPrefetchArgumentVariationName[] = L"PrefetchArgument";
 
 // Registry key in which the PreRead field trial group is stored.
 const base::char16 kPreReadFieldTrialRegistryKey[] = L"\\PreReadFieldTrial";
@@ -47,12 +48,14 @@ void GetPreReadOptions(const base::string16& product_registry_path,
                        bool* no_pre_read,
                        bool* high_priority,
                        bool* only_if_cold,
-                       bool* prefetch_virtual_memory) {
+                       bool* prefetch_virtual_memory,
+                       bool* prefetch_argument) {
   DCHECK(!product_registry_path.empty());
   DCHECK(no_pre_read);
   DCHECK(high_priority);
   DCHECK(only_if_cold);
   DCHECK(prefetch_virtual_memory);
+  DCHECK(prefetch_argument);
 
   // Open the PreRead field trial's registry key.
   const base::string16 registry_path =
@@ -69,6 +72,7 @@ void GetPreReadOptions(const base::string16& product_registry_path,
       {kHighPriorityVariationName, high_priority},
       {kOnlyIfColdVariationName, only_if_cold},
       {kPrefetchVirtualMemoryVariationName, prefetch_virtual_memory},
+      {kPrefetchArgumentVariationName, prefetch_argument},

[gab, 2016/01/18 19:10:52]

Actually, /prefetch applies only to processes launched after the initial startup
phase during which we can't use Finch... so we could use the regular Finch
groups (no registry) for this one... WDYT?

I guess since we want to mix it with other prefetch experiments it's still best
to keep it here even though it's not necessary for this specific variation,
it'll make for easier analysis of variation mixes.

   };
 
   for (const auto& mapping : variations_mappings) {