New experiment without registry deletion

chrome/browser/shell_integration_win.cc

Index: chrome/browser/shell_integration_win.cc
diff --git a/chrome/browser/shell_integration_win.cc b/chrome/browser/shell_integration_win.cc
index 04bc80c220d314d2a3c7074f0c420cbde1eb233b..e023956c897a51c10daf979741b4bf84c32ba4f3 100644
--- a/chrome/browser/shell_integration_win.cc
+++ b/chrome/browser/shell_integration_win.cc
@@ -56,6 +56,15 @@ namespace {
 const wchar_t kAppListAppNameSuffix[] = L"AppList";
 
 const char kAsyncSetAsDefaultExperimentName[] = "AsyncSetAsDefault";
+// A prefix shared by multiple groups that kicks off the generic set-as-default

[gab, 2016/01/12 01:26:46]

nit: I guess for consistency s/set-as-default/AsyncSetAsDefault/

(sorry, I know I wrote this suggestion, but seeing it in context now brought
this to my eye...)

[Patrick Monette, 2016/01/12 01:29:33]

Done.

+// experiment.
+const char kAsyncSetAsDefaultExperimentEnabledGroupPrefix[] = "Enabled";
+// One of the group names for the AsyncSetAsDefault experiment. Unlike other
+// "Enabled" groups, this group doesn't reset the current default browser choice
+// in the registry.
+const char kAsyncSetAsDefaultExperimentEnabledNoRegistryGroupName[] =
+    "EnabledNoRegistry";
+
 const char kEnableAsyncSetAsDefault[] = "enable-async-set-as-default";
 const char kDisableAsyncSetAsDefault[] = "disable-async-set-as-default";
 
@@ -279,13 +288,24 @@ bool IsAsyncSetAsDefaultEnabled() {
   // Note: It's important to query the field trial state first, to ensure that
   // UMA reports the correct group.
   const std::string group_name =
-      base::FieldTrialList::FindFullName("AsyncSetAsDefault");
+      base::FieldTrialList::FindFullName(kAsyncSetAsDefaultExperimentName);
   if (CommandLine::ForCurrentProcess()->HasSwitch(kDisableAsyncSetAsDefault))
     return false;
   if (CommandLine::ForCurrentProcess()->HasSwitch(kEnableAsyncSetAsDefault))
     return true;
 
-  return base::StartsWith(group_name, "Enabled", base::CompareCase::SENSITIVE);
+  return base::StartsWith(group_name,
+                          kAsyncSetAsDefaultExperimentEnabledGroupPrefix,
+                          base::CompareCase::SENSITIVE);
+}
+
+// Returns true if the default browser choice should be reset for the current
+// user.
+bool ShouldResetDefaultBrowser() {
+  return !base::StartsWith(
+      base::FieldTrialList::FindFullName(kAsyncSetAsDefaultExperimentName),
+      kAsyncSetAsDefaultExperimentEnabledNoRegistryGroupName,
+      base::CompareCase::SENSITIVE);
 }
 
 bool RegisterBrowser() {
@@ -720,7 +740,8 @@ bool ShellIntegration::DefaultBrowserWorker::SetAsDefaultBrowserAsynchronous() {
   if (!RegisterBrowser())
     return false;
 
-  ResetDefaultBrowser();
+  if (ShouldResetDefaultBrowser())
+    ResetDefaultBrowser();
 
   base::CommandLine cmdline(base::FilePath(L"openwith.exe"));
   cmdline.AppendArgNative(StartupBrowserCreator::GetDefaultBrowserUrl());