Determine the Win10-specific Welcome page variant to display

chrome/browser/ui/webui/welcome_win10_handler.cc

 // Copyright 2016 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/ui/webui/welcome_win10_handler.h"
 
-#include <string>
-
 #include "base/bind.h"
 #include "chrome/browser/shell_integration.h"
 #include "chrome/common/url_constants.h"
+#include "chrome/grit/generated_resources.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "url/gurl.h"
 
-WelcomeWin10Handler::WelcomeWin10Handler() = default;
+WelcomeWin10Handler::WelcomeWin10Handler() {
+  // The check is started as early as possible because waiting for the page to
+  // be fully loaded is unnecessarily wasting time.
+  StartIsPinnedToTaskbarCheck();
+}
 
 WelcomeWin10Handler::~WelcomeWin10Handler() = default;
 
-// Override from WebUIMessageHandler.
 void WelcomeWin10Handler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       "handleSetDefaultBrowser",
       base::Bind(&WelcomeWin10Handler::HandleSetDefaultBrowser,
                  base::Unretained(this)));
   web_ui()->RegisterMessageCallback(
       "handleContinue",
       base::Bind(&WelcomeWin10Handler::HandleContinue, base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
+      "getPinnedToTaskbarState",
+      base::Bind(&WelcomeWin10Handler::HandleGetPinnedToTaskbarState,
+                 base::Unretained(this)));
+}
+
+void WelcomeWin10Handler::HandleGetPinnedToTaskbarState(
+    const base::ListValue* args) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  AllowJavascript();
+
+  CHECK_EQ(1U, args->GetSize());
+  // Save the callback id so that the result can be sent back when it is
+  // available.
+  CHECK(args->GetString(0, &pinned_state_callback_id_));
+
+  // Send back the result if it is already available.
+  if (pinned_state_result_) {
+    SendPinnedToTaskbarStateResult();
+    return;
+  }
+
+  // Only wait for a small amount of time for the result. If the timer fires,
+  // it will be assumed that Chrome is pinned to the taskbar.
+  static constexpr base::TimeDelta kPinnedToTaskbarTimeout =

[michaelpg, 2016/10/31 21:04:59]

so it seems this is allowed because it's |constexpr|, but why make this static
at all?

[Patrick Monette, 2016/10/31 22:33:49]

Removed static.

+      base::TimeDelta::FromMilliseconds(200);
+  timer_.Start(FROM_HERE, kPinnedToTaskbarTimeout,
+               base::Bind(&WelcomeWin10Handler::OnIsPinnedToTaskbarDetermined,
+                          base::Unretained(this), true));
 }
 
 void WelcomeWin10Handler::HandleSetDefaultBrowser(const base::ListValue* args) {
   // The worker owns itself.
   (new shell_integration::DefaultBrowserWorker(
        shell_integration::DefaultWebClientWorkerCallback()))
       ->StartSetAsDefault();
 }
 
 void WelcomeWin10Handler::HandleContinue(const base::ListValue* args) {
   web_ui()->GetWebContents()->GetController().LoadURL(
       GURL(chrome::kChromeUINewTabURL), content::Referrer(),
       ui::PageTransition::PAGE_TRANSITION_LINK, std::string());
 }
+
+void WelcomeWin10Handler::StartIsPinnedToTaskbarCheck() {
+  // Start the utility process that will handle the IsPinnedToTaskbar() call.
+  client_.reset(new content::UtilityProcessMojoClient<mojom::ShellHandler>(
+      l10n_util::GetStringUTF16(IDS_UTILITY_PROCESS_SHELL_HANDLER_NAME)));
+
+  // Assume that Chrome is pinned to the taskbar if an error occurs.
+  client_->set_error_callback(
+      base::Bind(&WelcomeWin10Handler::OnIsPinnedToTaskbarDetermined,
+                 base::Unretained(this), true));
+  client_->set_disable_sandbox();
+  client_->Start();
+
+  client_->service()->IsPinnedToTaskbar(base::Bind(
+      &WelcomeWin10Handler::OnIsPinnedToTaskbarResult, base::Unretained(this)));
+}
+
+void WelcomeWin10Handler::OnIsPinnedToTaskbarResult(bool succeeded,
+                                                    bool is_pinned_to_taskbar) {
+  OnIsPinnedToTaskbarDetermined(succeeded && is_pinned_to_taskbar);
+}
+
+void WelcomeWin10Handler::OnIsPinnedToTaskbarDetermined(
+    bool is_pinned_to_taskbar) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+
+  // Reset the client and the timer to make sure this function only gets called
+  // once.
+  client_.reset();
+  timer_.Stop();
+
+  pinned_state_result_ = is_pinned_to_taskbar;
+
+  // If the page already called getPinnedToTaskbarState(), the result can be
+  // sent back.
+  if (!pinned_state_callback_id_.empty())
+    SendPinnedToTaskbarStateResult();
+}
+
+void WelcomeWin10Handler::SendPinnedToTaskbarStateResult() {
+  ResolveJavascriptCallback(
+      base::StringValue(pinned_state_callback_id_),
+      base::FundamentalValue(pinned_state_result_.value()));
+}