New experiment without registry deletion

chrome/browser/shell_integration_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/shell_integration.h"
 
 #include <windows.h>
 #include <shlwapi.h>
 #include <shobjidl.h>
 #include <propkey.h>  // Needs to come after shobjidl.h.
@@ skipping 38 matching lines @@
 #include "components/variations/variations_associated_data.h"
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
 
 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";
 
 // Helper function for ShellIntegration::GetAppId to generates profile id
 // from profile path. "profile_id" is composed of sanitized basenames of
 // user data dir and profile dir joined by a ".".
 base::string16 GetProfileIdFromPath(const base::FilePath& profile_path) {
   // Return empty string if profile_path is empty
   if (profile_path.empty())
     return base::string16();
@@ skipping 203 matching lines @@
   }
 }
 
 // Returns true if the AsyncSetAsDefault field trial is activated.
 bool IsAsyncSetAsDefaultEnabled() {
   using base::CommandLine;
 
   // 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);
 }
 
 bool RegisterBrowser() {
   base::FilePath chrome_exe;
   if (!PathService::Get(base::FILE_EXE, &chrome_exe)) {
     NOTREACHED() << "Error getting app exe path";
     return false;
   }
   BrowserDistribution* dist = BrowserDistribution::GetDistribution();
 
   return ShellUtil::RegisterChromeBrowser(dist, chrome_exe, base::string16(),
                                           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
 bool ShellIntegration::IsSetAsDefaultAsynchronous() {
   return base::win::GetVersion() >= base::win::VERSION_WIN10 &&
          IsAsyncSetAsDefaultEnabled();
 }
 
 bool ShellIntegration::SetAsDefaultBrowser() {
   base::FilePath chrome_exe;
@@ skipping 400 matching lines @@
 
 // static
 bool ShellIntegration::DefaultBrowserWorker::SetAsDefaultBrowserAsynchronous() {
   DCHECK(IsSetAsDefaultAsynchronous());
 
   // Registers chrome.exe as a browser on Windows to make sure it will be shown
   // in the "How would you like to open this?" prompt.
   if (!RegisterBrowser())
     return false;
 
-  ResetDefaultBrowser();
+  if (ShouldResetDefaultBrowser())
+    ResetDefaultBrowser();
 
   base::CommandLine cmdline(base::FilePath(L"openwith.exe"));
   cmdline.AppendArgNative(StartupBrowserCreator::GetDefaultBrowserUrl());
   return base::LaunchProcess(cmdline, base::LaunchOptions()).IsValid();
 }