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..0744ed6ea6a98d748eb24f9b2d10d5fd1212ccd3 100644
--- a/chrome/browser/shell_integration_win.cc
+++ b/chrome/browser/shell_integration_win.cc
@@ -56,6 +56,10 @@ namespace {
 const wchar_t kAppListAppNameSuffix[] = L"AppList";
 
 const char kAsyncSetAsDefaultExperimentName[] = "AsyncSetAsDefault";
+// One of the group name for the AsynSetAsDefault experiment. This group disable
+// the default browser choice reset for the async flow. The other enabled group
+// is "EnabledFull" where the default browser choice is reset.

[gab, 2016/01/12 01:09:04]

// 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.

(i.e. don't explicitly mention a group name that is server-side only and cut a
bit of the rest to make it more succinct, WDYT?)

[Patrick Monette, 2016/01/12 01:22:03]

I like it.

+const char kEnabledNoRegistryGroupName[] = "EnabledNoRegistry";

[gab, 2016/01/12 01:09:04]

kAsyncSetAsDefaultExperimentEnabledNoRegistryGroupName ?

Man this is long but I feel these constants should all have an experiment
specific prefix.

[gab, 2016/01/12 01:09:04]

Also add 

// A prefix shared by multiple groups that kicks off the generic set-as-default
experiment.
const char kAsyncSetAsDefaultExperimentEnabledGroupPrefix[] = "Enabled";

(i.e. the advantage of specifying "EnabledNoRegistry" as a constant is only
there when all other variants are alongside it)

[Patrick Monette, 2016/01/12 01:22:03]

Done.

 const char kEnableAsyncSetAsDefault[] = "enable-async-set-as-default";
 const char kDisableAsyncSetAsDefault[] = "disable-async-set-as-default";
 
@@ -279,7 +283,7 @@ 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))
@@ -300,6 +304,14 @@ bool RegisterBrowser() {
                                           true);
 }
 
+// Returns true if the default browser choice should be reset for the current
+// user.
+bool ShouldResetDefaultBrowser() {

[gab, 2016/01/12 01:09:04]

Put this below IsAsyncSetAsDefaultEnabled() to keep related methods together?

[Patrick Monette, 2016/01/12 01:22:03]

Done.

+  return !base::StartsWith(
+      base::FieldTrialList::FindFullName(kAsyncSetAsDefaultExperimentName),
+      kEnabledNoRegistryGroupName, base::CompareCase::SENSITIVE);
+}
+
 }  // namespace
 
 // static
@@ -720,7 +732,8 @@ bool ShellIntegration::DefaultBrowserWorker::SetAsDefaultBrowserAsynchronous() {
   if (!RegisterBrowser())
     return false;
 
-  ResetDefaultBrowser();
+  if (ShouldResetDefaultBrowser())
+    ResetDefaultBrowser();
 
   base::CommandLine cmdline(base::FilePath(L"openwith.exe"));
   cmdline.AppendArgNative(StartupBrowserCreator::GetDefaultBrowserUrl());