Determine the Win10-specific Welcome page variant to display

chrome/browser/ui/webui/welcome_win10_handler.cc

Index: chrome/browser/ui/webui/welcome_win10_handler.cc
diff --git a/chrome/browser/ui/webui/welcome_win10_handler.cc b/chrome/browser/ui/webui/welcome_win10_handler.cc
index de4167ad0b359e2850c9f2c8e7544b8e42322247..02df7c892607c3575f4d20cf470b5fc3dd61f781 100644
--- a/chrome/browser/ui/webui/welcome_win10_handler.cc
+++ b/chrome/browser/ui/webui/welcome_win10_handler.cc
@@ -9,13 +9,15 @@
 #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/web_contents.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "url/gurl.h"
 
 WelcomeWin10Handler::WelcomeWin10Handler() = default;
 
 WelcomeWin10Handler::~WelcomeWin10Handler() = default;
 
-// Override from WebUIMessageHandler.
 void WelcomeWin10Handler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       "handleSetDefaultBrowser",
@@ -24,6 +26,41 @@ void WelcomeWin10Handler::RegisterMessages() {
   web_ui()->RegisterMessageCallback(
       "handleContinue",
       base::Bind(&WelcomeWin10Handler::HandleContinue, base::Unretained(this)));
+  web_ui()->RegisterMessageCallback(
+      "handleIsPinnedToTaskbar",
+      base::Bind(&WelcomeWin10Handler::HandleIsPinnedToTaskbar,
+                 base::Unretained(this)));
+}
+
+void WelcomeWin10Handler::HandleIsPinnedToTaskbar(const base::ListValue* args) {
+  AllowJavascript();
+
+  CHECK_EQ(1U, args->GetSize());
+  std::string callback_id;
+  CHECK(args->GetString(0, &callback_id));
+
+  // Assume that Chrome is pinned to the taskbar if an error occured while
+  // checking or if the timeout is hit.
+  base::Closure on_error_callback =
+      base::Bind(&WelcomeWin10Handler::OnIsPinnedToTaskbarDetermined,
+                 base::Unretained(this), callback_id, true);
+
+  constexpr base::TimeDelta kPinnedToTaskbarTimeout =
+      base::TimeDelta::FromMilliseconds(2000);

[tmartino, 2016/10/28 15:18:04]

2s seems quite high.

[Patrick Monette, 2016/10/28 21:21:37]

I've put 200ms. On my debug version of Chrome, the result is always available
before getPinnedToTaskbarState() is called, so it should be fine.

+  // Set a timeout.
+  timer_.Start(FROM_HERE, kPinnedToTaskbarTimeout, on_error_callback);
+
+  // Start the utility process that will handle the IsPinnedToTaskbar() call.

[tmartino, 2016/10/28 15:18:04]

Would it be possible to start the check in the ctor and cache the result? Then
when the page asks whether or not we're pinned, we either returned the cached
value if we have it, or kick off the timer and do the callback at the first of
{result returned, timer expires}.

(Feel free to push back if you don't think the possible perf improvement would
justify the added complexity.)

[Patrick Monette, 2016/10/28 21:21:37]

Seems reasonable. Done.

+  client_.reset(new content::UtilityProcessMojoClient<mojom::ShellHandler>(
+      l10n_util::GetStringUTF16(IDS_UTILITY_PROCESS_SHELL_HANDLER_NAME)));
+
+  client_->set_error_callback(on_error_callback);
+  client_->set_disable_sandbox();
+  client_->Start();
+
+  client_->service()->IsPinnedToTaskbar(
+      base::Bind(&WelcomeWin10Handler::OnIsPinnedToTaskbarResult,
+                 base::Unretained(this), callback_id));
 }
 
 void WelcomeWin10Handler::HandleSetDefaultBrowser(const base::ListValue* args) {
@@ -38,3 +75,22 @@ void WelcomeWin10Handler::HandleContinue(const base::ListValue* args) {
       GURL(chrome::kChromeUINewTabURL), content::Referrer(),
       ui::PageTransition::PAGE_TRANSITION_LINK, std::string());
 }
+
+void WelcomeWin10Handler::OnIsPinnedToTaskbarResult(
+    const std::string& callback_id,
+    bool succeeded,
+    bool is_pinned_to_taskbar) {
+  OnIsPinnedToTaskbarDetermined(callback_id, succeeded && is_pinned_to_taskbar);
+}
+
+void WelcomeWin10Handler::OnIsPinnedToTaskbarDetermined(
+    const std::string& callback_id,
+    bool is_pinned_to_taskbar) {
+  // Reset the client and the timer to make sure this function only gets called
+  // once.
+  client_.reset();
+  timer_.Stop();
+
+  ResolveJavascriptCallback(base::StringValue(callback_id),
+                            base::FundamentalValue(is_pinned_to_taskbar));
+}