Bug 1584988 - Only allow files to be dropped onto HAR overlay r=Honza

Differential Revision: https://phabricator.services.mozilla.com/D48982

--HG--
extra : moz-landing-system : lando

devtools/client/netmonitor/src/components/DropHarHandler.js

@@ -51,6 +51,10 @@ class DropHarHandler extends Component {
 
   onDragEnter(event) {
     event.preventDefault();
+    if (event.dataTransfer.files.length === 0) {
+      return;
+    }
+
     startDragging(findDOMNode(this));
   }
 

devtools/client/shared/components/tabs/Tabs.js

@@ -232,6 +232,13 @@ define(function(require, exports, module) {
       }
     }
 
+    onMouseDown(event) {
+      // Prevents click-dragging the tab headers
+      if (event) {
+        event.preventDefault();
+      }
+    }
+
     // API
 
     setActive(index) {
@@ -322,6 +329,7 @@ define(function(require, exports, module) {
                 "aria-selected": isTabSelected,
                 role: "tab",
                 onClick: this.onClickTab.bind(this, index),
+                onMouseDown: this.onMouseDown.bind(this),
               },
               title,
               badge && !isTabSelected && showBadge()