Implementing TabManager extensions API Discard Function.

chrome/browser/extensions/api/tabs/tabs_api.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/extensions/api/tabs/tabs_api.h"
 
 #include <stddef.h>
 #include <algorithm>
 #include <limits>
 #include <memory>
@@ skipping 2150 matching lines @@
   api::tabs::ZoomSettings zoom_settings;
   ZoomModeToZoomSettings(zoom_mode, &zoom_settings);
   zoom_settings.default_zoom_factor.reset(new double(
       content::ZoomLevelToZoomFactor(zoom_controller->GetDefaultZoomLevel())));
 
   results_ = api::tabs::GetZoomSettings::Results::Create(zoom_settings);
   SendResponse(true);
   return true;
 }
 
+ExtensionFunction::ResponseAction TabsDiscardFunction::Run() {
+  std::unique_ptr<tabs::Discard::Params> params(
+      tabs::Discard::Params::Create(*args_));
+  EXTENSION_FUNCTION_VALIDATE(params);
+
+  WebContents* contents = nullptr;
+  Profile* profile = Profile::FromBrowserContext(browser_context());
+  // If |tab_id| is given, find the web_contents respective to it.
+  // Otherwise invoke discard function in TabManager with null web_contents
+  // that will discard the least important tab.
+  if (params->tab_id) {
+    int tab_id = *params->tab_id;
+    if (!GetTabById(tab_id, profile, include_incognito(), nullptr, nullptr,
+                    &contents, nullptr, &error_)) {
+      return RespondNow(Error(error_));
+    }
+  }
+  // Discard the tab.
+  contents =
+      g_browser_process->GetTabManager()->DiscardTabByExtension(contents);
+
+  // Create result to be returned. We have to return a Tab object,
+  // then a default object is created and replaced with the real
+  // tab in case of success (contents is not null).
+  std::unique_ptr<tabs::Tab> tab(new tabs::Tab);

[Devlin, 2016/07/22 18:39:19]

This won't be undefined, then, it'll be a tab object with default properties.

This also implies that there's a test missing (passing in an invalid tab id). ;)

[Anderson Silva, 2016/07/22 20:18:25]

Yes, it's a tab object. I tested in an extension and the fields of the object
are undefined though.
I'm trying to return the tab as undefined but can't get it working or find an
example.
If I don't return anything, it throws an exception because the Tab is required.
Tests depend on this so I'm hold.

Do you know if this is feasible? Or should we change function description (in
the json) setting the returned Tab as optional?

Thanks

[Devlin, 2016/07/22 20:20:53]

^^ This. :)  Marking the field as optional and then using an empty unique_ptr
should do the trick, I think.

[Anderson Silva, 2016/07/22 22:50:14]

Done.
Empty unique_ptr crashes but no arguments works just fine.
Added two new tests for this. One that catches the error when passed invalid id
and another that makes sure the result is undefined when no tab is discarded.

+  if (contents)
+    tab = ExtensionTabUtil::CreateTabObject(contents);
+  return RespondNow(ArgumentList(tabs::Discard::Results::Create(*tab)));
+}
+
+TabsDiscardFunction::TabsDiscardFunction() {}
+TabsDiscardFunction::~TabsDiscardFunction() {}
+
 }  // namespace extensions