Setting chrome as the default browser is now fixed on Windows 10

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 07f7b4b9f8e465faaad7240654e82ebedbb91644..fc8b207f52808b1e13ed8be6f3fde2648b6faab0 100644
--- a/chrome/browser/shell_integration_win.cc
+++ b/chrome/browser/shell_integration_win.cc
@@ -5,6 +5,7 @@
 #include "chrome/browser/shell_integration.h"
 
 #include <windows.h>
+#include <shellapi.h>
 #include <shlwapi.h>
 #include <shobjidl.h>
 #include <propkey.h>  // Needs to come after shobjidl.h.
@@ -14,6 +15,8 @@
 #include "base/files/file_enumerator.h"
 #include "base/files/file_util.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/field_trial.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/path_service.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -25,6 +28,7 @@
 #include "base/win/shortcut.h"
 #include "base/win/windows_version.h"
 #include "chrome/browser/policy/policy_path_parser.h"
+#include "chrome/browser/ui/startup/startup_browser_creator.h"
 #include "chrome/browser/web_applications/web_app.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/chrome_paths_internal.h"
@@ -38,6 +42,7 @@
 #include "chrome/installer/util/util_constants.h"
 #include "chrome/installer/util/work_item.h"
 #include "chrome/installer/util/work_item_list.h"
+#include "components/variations/variations_associated_data.h"
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
@@ -45,6 +50,12 @@ using content::BrowserThread;
 namespace {
 
 const wchar_t kAppListAppNameSuffix[] = L"AppList";
+const wchar_t kSetDefaultBrowserHelpUrl[] =
+    L"https://support.google.com/chrome?p=default_browser";
+
+const char kAsyncSetAsDefaultExperimentName[] = "AsyncSetAsDefault";
+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
@@ -240,8 +251,54 @@ ShellIntegration::DefaultWebClientState
   }
 }
 
+// Resets the default browser choice for the current user.
+void ResetDefaultBrowser() {
+  static const wchar_t* kUrlAssociationKeyFormats[] = {
+      L"SOFTWARE\\Microsoft\\Windows\\Shell\\Associations\\UrlAssociations\\"
+      L"%ls\\UserChoice",
+      L"SOFTWARE\\Microsoft\\Windows\\Roaming\\OpenWith\\UrlAssociations\\"
+      L"%ls\\UserChoice"};
+  static const wchar_t* kProtocols[] = {L"http", L"https"};
+
+  for (const wchar_t* format : kUrlAssociationKeyFormats) {
+    for (const wchar_t* protocol : kProtocols) {
+      base::win::RegKey registry_key(
+          HKEY_CURRENT_USER, base::StringPrintf(format, protocol).c_str(),
+          KEY_WRITE);
+      registry_key.DeleteValue(L"Hash");
+    }
+  }
+}
+
+// Returns true if the AsyncSetAsDefault field trial is activated.
+bool IsAsyncSetAsDefaultEnabled() {
+  using base::CommandLine;
+
+  const std::string group_name =
+      base::FieldTrialList::FindFullName("AsyncSetAsDefault");
+  if (CommandLine::ForCurrentProcess()->HasSwitch(kDisableAsyncSetAsDefault))
+    return false;
+  if (CommandLine::ForCurrentProcess()->HasSwitch(kEnableAsyncSetAsDefault))
+    return true;
+
+  return base::StartsWith(group_name, "Enabled", base::CompareCase::SENSITIVE);
+}
+
 }  // namespace
 
+// static
+bool ShellIntegration::IsSetAsDefaultAsynchronous() {
+  return base::win::GetVersion() >= base::win::VERSION_WIN10 &&
+         IsAsyncSetAsDefaultEnabled();
+}
+
+void ShellIntegration::SetAsDefaultBrowserAsynchronous() {
+  DCHECK(base::win::GetVersion() >= base::win::VERSION_WIN10);
+
+  ResetDefaultBrowser();
+  ShellExecute(0, 0, kSetDefaultBrowserHelpUrl, 0, 0, SW_SHOW);
+}
+
 ShellIntegration::DefaultWebClientSetPermission
     ShellIntegration::CanSetAsDefaultBrowser() {
   BrowserDistribution* distribution = BrowserDistribution::GetDistribution();
@@ -251,6 +308,8 @@ ShellIntegration::DefaultWebClientSetPermission
 
   if (ShellUtil::CanMakeChromeDefaultUnattended())
     return SET_DEFAULT_UNATTENDED;
+  else if (IsSetAsDefaultAsynchronous())
+    return SET_DEFAULT_ASYNCHRONOUS;
   else
     return SET_DEFAULT_INTERACTIVE;
 }
@@ -588,3 +647,58 @@ base::FilePath ShellIntegration::GetStartMenuShortcut(
 
   return base::FilePath();
 }
+
+void ShellIntegration::DefaultBrowserWorker::InitializeSetAsDefault() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  if (IsSetAsDefaultAsynchronous()) {
+    StartupBrowserCreator::AddUrlFilter(

[grt (UTC plus 2), 2015/09/22 18:21:47]

this seems like a good place to put the comment explaining how the filter and
timeout work.

[Patrick Monette, 2015/09/23 22:40:44]

Done.

+        GURL(kSetDefaultBrowserHelpUrl),
+        base::Bind(&DefaultBrowserWorker::CompleteSetAsDefault, this, true));
+
+    // Remember the start time.
+    start_time_ = base::TimeTicks::Now();
+
+    // Start the timer.
+    if (!async_timer_)
+      async_timer_.reset(new base::OneShotTimer<DefaultWebClientWorker>());
+
+    base::TimeDelta timer_duration = base::TimeDelta::FromMinutes(2);
+    std::string value = variations::GetVariationParamValue(
+        kAsyncSetAsDefaultExperimentName, "TimerDuration");
+    if (!value.empty())
+      timer_duration = base::TimeDelta::FromSeconds(std::atoi(value.c_str()));

[grt (UTC plus 2), 2015/09/22 18:21:47]

atoi -> base::StringToInt. it has interesting failure modes, so maybe something
like:

  int seconds = 0;
  if (!value.empty())
    base::StringToInt(value, &seconds);
  if (seconds)
    timer_duration = base::TimeDelta::FromSeconds(seconds);

[Patrick Monette, 2015/09/23 22:40:44]

Done.

+
+    async_timer_->Start(
+        FROM_HERE, timer_duration,
+        base::Bind(&DefaultBrowserWorker::CompleteSetAsDefault, this, false));
+  }
+}
+
+bool ShellIntegration::DefaultBrowserWorker::UninitializeSetAsDefault(
+    bool succeeded) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  if (IsSetAsDefaultAsynchronous()) {
+    GURL default_browser_help_url(kSetDefaultBrowserHelpUrl);
+    if (!async_timer_) {
+      // If the timer isnt set, that means it has already fired and
+      // the observer should not be notified again.
+      DCHECK(!StartupBrowserCreator::UrlFilterExists(default_browser_help_url));
+      return false;
+    }
+
+    // Record the duration from starting to set as default browser to now.
+    UMA_HISTOGRAM_BOOLEAN("AsyncSetAsDefault.Succeeded", succeeded);
+    UMA_HISTOGRAM_TIMES("AsyncSetAsDefault.Duration",
+                        base::TimeTicks::Now() - start_time_);
+
+    // Destroy timer.
+    async_timer_.reset();
+
+    // Remove filter if it exists.
+    if (StartupBrowserCreator::UrlFilterExists(default_browser_help_url))
+      StartupBrowserCreator::RemoveUrlFilter(default_browser_help_url);
+  }
+  return true;
+}