Noissue - Check for devtools.panels API support

devtools.js

Index: devtools.js
===================================================================
--- a/devtools.js
+++ b/devtools.js
@@ -14,46 +14,52 @@
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 let panelWindow = null;
 
-chrome.runtime.sendMessage(
-  {
-    type: "prefs.get",
-    key: "show_devtools_panel"
-  },
-  enabled =>
-  {
-    if (enabled)
+// Versions of Firefox before 54 do not support the devtools.panels API; on
+// these platforms, even when the option is enabled, we cannot show the
+// devtools panel.
+if ("panels" in chrome.devtools)
+{
+  chrome.runtime.sendMessage(
     {
-      chrome.devtools.panels.create(
-        "Adblock Plus",
-        "icons/detailed/abp-48.png",
-        "devtools-panel.html",
-        panel =>
-        {
-          panel.onShown.addListener(window =>
+      type: "prefs.get",
+      key: "show_devtools_panel"
+    },
+    enabled =>
+    {
+      if (enabled)
+      {
+        chrome.devtools.panels.create(
+          "Adblock Plus",
+          "icons/detailed/abp-48.png",
+          "devtools-panel.html",
+          panel =>
           {
-            panelWindow = window;
-          });
+            panel.onShown.addListener(window =>
+            {
+              panelWindow = window;
+            });
 
-          panel.onHidden.addListener(window =>
-          {
-            panelWindow = null;
-          });
+            panel.onHidden.addListener(window =>
+            {
+              panelWindow = null;
+            });
 
-          if (panel.onSearch)
-          {
-            panel.onSearch.addListener((eventName, queryString) =>
+            if (panel.onSearch)
             {
-              if (panelWindow)
-                panelWindow.postMessage({type: eventName, queryString}, "*");
-            });
+              panel.onSearch.addListener((eventName, queryString) =>
+              {
+                if (panelWindow)
+                  panelWindow.postMessage({type: eventName, queryString}, "*");
+              });
+            }
           }
-        }
-      );
+        );
+      }
     }
-  }
-);
+  );
+}