Adding JS and C++ handlers for events on new Welcome page.

chrome/browser/ui/webui/welcome_ui.cc

Index: chrome/browser/ui/webui/welcome_ui.cc
diff --git a/chrome/browser/ui/webui/welcome_ui.cc b/chrome/browser/ui/webui/welcome_ui.cc
index 7c5ffe117b60636bc418bbce20ecbc3c2a720865..b09b6d33de7c84837da16d1672f2d3ac82878ce3 100644
--- a/chrome/browser/ui/webui/welcome_ui.cc
+++ b/chrome/browser/ui/webui/welcome_ui.cc
@@ -5,26 +5,124 @@
 #include "chrome/browser/ui/webui/welcome_ui.h"
 
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/signin/profile_oauth2_token_service_factory.h"
+#include "chrome/browser/signin/signin_manager_factory.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_finder.h"
+#include "chrome/browser/ui/browser_navigator.h"
+#include "chrome/browser/ui/profile_chooser_constants.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/grit/browser_resources.h"
 #include "chrome/grit/chrome_unscaled_resources.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
+#include "components/signin/core/browser/profile_oauth2_token_service.h"
+#include "components/signin/core/browser/signin_manager.h"
+#include "components/signin/core/browser/signin_metrics.h"
 #include "content/public/browser/web_ui_data_source.h"
+#include "content/public/browser/web_ui_message_handler.h"
+#include "google_apis/gaia/oauth2_token_service.h"
 #include "ui/base/l10n/l10n_util.h"
+#include "ui/base/page_transition_types.h"
 #include "ui/resources/grit/webui_resources.h"
 
 namespace {
 
+enum WelcomeResult {
+  DEFAULT = 0,
+  SIGNED_IN,  // User clicked the "Sign In" button and completed sign-in.
+  DECLINED    // User clicked the "No Thanks" button.
+};
+
 // A URL ending in /1 indicates that we should modify the page to use the
 // "Take Chrome Everywhere" text.
 const char* kEverywhereVariantPath = "/1";

[anthonyvd, 2016/09/19 17:12:16]

Why not a descriptive GET style param?

[tmartino, 2016/09/19 22:37:04]

If you don't mind me asking, what would the gain be? This way I can do a simple
equality check. Using a GET param would involve parsing (to separate out the
key/value/delimiter) which seems to add a lot of complexity for little benefit
when we only have one variant that's either on or off.

I suppose we could do a literal string check against the whole parameter string
(e.g., if (url.query() == "variant=everywhere")) but then it's logically
equivalent to this anyway.

[anthonyvd, 2016/09/21 16:17:56]

It's just more self-documenting that way. You can also use
net::GetValueForKeyInQuery for easy parsing. Something like:

std::string value;
if (net::GetValueForKeyInQuery(url, "take_everywhere", &value) && value == "1")
{
  // Show the "Take Everywhere" variant
}

alternately, if we expect to have more variants at some point:

std::string value;
if (net::GetValueForKeyInQuery(url, "variant", &value) && value ==
"take_everywhere") {
  // Show the "Take Everywhere" variant
} 

[tmartino, 2016/09/22 20:32:09]

Opted for the latter.

 
+const char* kHandleActivateSignIn = "handleActivateSignIn";

[anthonyvd, 2016/09/19 17:12:15]

Message name strings tend to be just inlined when registered so you don't need
to define them as constants.

+const char* kHandleUserDecline = "handleUserDecline";
+
+class WelcomeHandler : public content::WebUIMessageHandler,

[anthonyvd, 2016/09/19 17:12:15]

Your handler should be in a separate file for consistency with other handlers.

+                       public OAuth2TokenService::Observer {
+ public:
+  explicit WelcomeHandler(content::WebUI* web_ui) {
+    profile_ = Profile::FromWebUI(web_ui);

[anthonyvd, 2016/09/19 17:12:16]

Prefer initializer lists over initializing in the ctor body.

+    oauth2_token_service_ =
+        ProfileOAuth2TokenServiceFactory::GetForProfile(profile_);
+    if (oauth2_token_service_)

[anthonyvd, 2016/09/19 17:12:16]

The Service Factories initialize services in GetForProfile if they don't exist
already so that if() is likely superfluous.

+      oauth2_token_service_->AddObserver(this);
+
+    browser_ = chrome::FindBrowserWithWebContents(web_ui->GetWebContents());
+    result_ = WelcomeResult::DEFAULT;
+    user_has_clicked_signin_ = false;
+  }
+
+  ~WelcomeHandler() override {
+    if (oauth2_token_service_)
+      oauth2_token_service_->RemoveObserver(this);
+    // TODO(tmartino): Log to UMA according to WelcomeResult.
+  }
+
+  // Override from OAuth2TokenService::Observer. Occurs when a new auth token is
+  // available.
+  void OnRefreshTokenAvailable(const std::string& account_id) override {
+    if (user_has_clicked_signin_) {

[anthonyvd, 2016/09/19 17:12:15]

What happens if the user has this page up and signs in through the User Menu?
Shouldn't this always go to the NTP when the user signs in regardless of source?

[tmartino, 2016/09/19 22:37:04]

I was torn on this. Either way it's kind of jarring for the user. Either:

(1) Page navigation happens unexpectedly, or
(2) The page doesn't disappear, but the "sign in" button acts as a no-op
navigation button

I opted for the latter. WDYT?

[anthonyvd, 2016/09/21 16:17:56]

Good point, I personally prefer (1) but I could see it either way. That's
something Design/PM should be able to settle.

[tmartino, 2016/09/22 20:32:09]

Brought this up and the consensus was to go with (1). Changed.

+      result_ = WelcomeResult::SIGNED_IN;
+      GoToNewTabPage();
+    }
+  }
+
+  // Handles backend events necessary when user clicks "Sign in."
+  void HandleActivateSignIn(const base::ListValue* args) {
+    user_has_clicked_signin_ = true;
+
+    if (SigninManagerFactory::GetForProfile(profile_)->IsAuthenticated()) {
+      // In general, this page isn't shown to signed-in users; however, if one
+      // should arrive here, then opening the sign-in dialog will likely lead
+      // to a crash. Thus, we just act like sign-in was "successful" and whisk
+      // them away to the NTP instead,
+      GoToNewTabPage();
+    } else {
+      browser_->ShowModalSigninWindow(
+          profiles::BubbleViewMode::BUBBLE_VIEW_MODE_GAIA_SIGNIN,
+          signin_metrics::AccessPoint::ACCESS_POINT_START_PAGE);
+    }
+  }
+
+  // Handles backend events necessary when user clicks "No thanks."
+  void HandleUserDecline(const base::ListValue* args) {
+    result_ = WelcomeResult::DECLINED;
+    GoToNewTabPage();
+  }
+
+  // Override from WebUIMessageHandler.
+  void RegisterMessages() override {
+    web_ui()->RegisterMessageCallback(
+        kHandleActivateSignIn, base::Bind(&WelcomeHandler::HandleActivateSignIn,
+                                          base::Unretained(this)));
+    web_ui()->RegisterMessageCallback(
+        kHandleUserDecline,
+        base::Bind(&WelcomeHandler::HandleUserDecline, base::Unretained(this)));
+  }
+
+  void GoToNewTabPage() {
+    chrome::NavigateParams params(browser_, GURL(chrome::kChromeUINewTabURL),
+                                  ui::PageTransition::PAGE_TRANSITION_LINK);
+    chrome::Navigate(&params);
+  }
+
+ private:
+  Profile* profile_;
+  Browser* browser_;
+  ProfileOAuth2TokenService* oauth2_token_service_;
+  WelcomeResult result_;
+  bool user_has_clicked_signin_;
+};
+
 }  // namespace
 
 WelcomeUI::WelcomeUI(content::WebUI* web_ui, const GURL& url)
     : content::WebUIController(web_ui) {
-  // TODO(tmartino): Create WelcomeHandler, and add here.
+  web_ui->AddMessageHandler(new WelcomeHandler(web_ui));
 
   content::WebUIDataSource* html_source =
       content::WebUIDataSource::Create(url.host());