Bug 1271084 - Apply ESLint autofixes to ignored /devtools files. r=tromey

For simple rules like function spacing, we can auto-fix these across the code
base so they are followed in a consistent way.

To generate this patch, I ran:

./mach eslint devtools --no-ignore --fix

After this, I reverted any changes to third party files that we really do want
to ignore.

MozReview-Commit-ID: 6Q8BApkAW20

devtools/client/performance/panel.js

@@ -29,7 +29,7 @@ PerformancePanel.prototype = {
    *         A promise that is resolved when the Performance tool
    *         completes opening.
    */
-  open: Task.async(function*() {
+  open: Task.async(function* () {
     if (this._opening) {
       return this._opening;
     }
@@ -77,7 +77,7 @@ PerformancePanel.prototype = {
     return this.toolbox.target;
   },
 
-  destroy: Task.async(function*() {
+  destroy: Task.async(function* () {
     // Make sure this panel is not already destroyed.
     if (this._destroyed) {
       return;