Add back button to chrome://devices

When settings in a window is enabled, add a back button to the devices
page. This helps because the window has no address bar. See bug for
screenshot.

Longer-term, the devices page should show as an overlay in Settings
rather than load as a new page.

RTL is not enabled for this page; see issue 386020.

BUG=384333
R=noamsml@chromium.org,oshima@chromium.org

+oshima@ for icon. Oshima, is theme_resources the right place for this?
+stevenjb@ for browser shenanigans in local_discovery_ui.cc.

Review URL: https://codereview.chromium.org/338423005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278376 0039d316-1c4b-4281-b951-d872f2087c98

chrome/app/theme/theme_resources.grd

@@ -140,6 +140,7 @@
       <structure type="chrome_scaled_image" name="IDR_BROWSER_ACTIONS_OVERFLOW" file="common/browser_actions_overflow_normal.png" />
       <structure type="chrome_scaled_image" name="IDR_BROWSER_ACTIONS_OVERFLOW_H" file="common/browser_actions_overflow_hover.png" />
       <structure type="chrome_scaled_image" name="IDR_BROWSER_ACTIONS_OVERFLOW_P" file="common/browser_actions_overflow_pressed.png" />
+      <structure type="chrome_scaled_image" name="IDR_CHEVRON_LEFT" file="common/chevron_left.png" />
       <structure type="chrome_scaled_image" name="IDR_CLOSE_BUTTON_MASK" file="common/close_button_mask.png" />
       <if expr="is_win">
         <structure type="chrome_scaled_image" name="IDR_CONFLICT_FAVICON" file="common/favicon_conflicts.png" />

chrome/browser/resources/local_discovery/local_discovery.css

@@ -112,4 +112,20 @@ section {
 
 .dialog-contents {
     padding-left: 17px;
-}
\ No newline at end of file
+}
+
+#back-button {
+  background: url('chrome://theme/IDR_CHEVRON_LEFT') left no-repeat;
+  margin-bottom: 25px;
+  margin-top: 6px;
+  padding-left: 23px;
+}
+
+html[dir='rtl'] #back-button {
+  transform: scaleX(-1);
+}
+
+html[dir='rtl'] #back-button span {
+  display: inline-block;
+  transform: scaleX(-1);
+}

chrome/browser/resources/local_discovery/local_discovery.html

@@ -78,6 +78,9 @@
     </div>
 
     <header>
+      <button id="back-button" class="link-button" hidden>
+        <span i18n-content="backButton"></span>
+      </button>
       <h1 i18n-content="devicesTitle"></h1>
     </header>
 

chrome/browser/resources/local_discovery/local_discovery.js

@@ -605,6 +605,13 @@ cr.define('local_discovery', function() {
       'click',
       registerOverlayLoginButtonClicked);
 
+    if (loadTimeData.valueExists('backButtonURL')) {
+      $('back-button').hidden = false;
+      $('back-button').addEventListener('click', function() {
+        window.location.href = loadTimeData.getString('backButtonURL');
+      });
+    }
+
     updateVisibility();
     document.addEventListener('visibilitychange', updateVisibility, false);
 

chrome/browser/ui/webui/local_discovery/local_discovery_ui.cc

@@ -5,10 +5,13 @@
 #include "chrome/browser/ui/webui/local_discovery/local_discovery_ui.h"
 
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/webui/local_discovery/local_discovery_ui_handler.h"
 #include "chrome/browser/ui/webui/metrics_handler.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
+#include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/browser/web_ui_data_source.h"
 #include "grit/browser_resources.h"
@@ -84,7 +87,7 @@ content::WebUIDataSource* CreateLocalDiscoveryHTMLSource() {
                              IDS_LOCAL_DISCOVERY_AVAILABLE_DEVICES);
   source->AddLocalizedString("myDevicesTitle",
                              IDS_LOCAL_DISCOVERY_MY_DEVICES);
-
+  source->AddLocalizedString("backButton", IDS_SETTINGS_TITLE);
 
   // Cloud print connector-related strings.
 #if defined(ENABLE_FULL_PRINTING) && !defined(OS_CHROMEOS)
@@ -112,8 +115,13 @@ content::WebUIDataSource* CreateLocalDiscoveryHTMLSource() {
 LocalDiscoveryUI::LocalDiscoveryUI(content::WebUI* web_ui)
     : WebUIController(web_ui) {
   // Set up the chrome://devices/ source.
-  Profile* profile = Profile::FromWebUI(web_ui);
-  content::WebUIDataSource::Add(profile, CreateLocalDiscoveryHTMLSource());
+  content::WebUIDataSource* source = CreateLocalDiscoveryHTMLSource();
+  Browser* browser =
+      chrome::FindBrowserWithWebContents(web_ui->GetWebContents());
+  // Show a back button pointing to Settings if the browser has no location bar.
+  if (browser && browser->is_trusted_source())
+    source->AddString("backButtonURL", chrome::kChromeUISettingsURL);
+  content::WebUIDataSource::Add(Profile::FromWebUI(web_ui), source);
 
   // TODO(gene): Use LocalDiscoveryUIHandler to send updated to the devices
   // page. For example