[AI Assistance] Fix edge case of div tag only selector

There is a special case in the SimpleSelector that
don't return div with classes.
So if we don't find a selector fall back to the
node tag

Fixed: 410484620
Change-Id: I391455a130360ef3c4052fecf62e88ad8148487c
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6454223
Reviewed-by: Ergün Erdoğmuş <ergunsh@chromium.org>
Auto-Submit: Nikolay Vitkov <nvitkov@chromium.org>
Commit-Queue: Ergün Erdoğmuş <ergunsh@chromium.org>
Commit-Queue: Nikolay Vitkov <nvitkov@chromium.org>

Author: Lightning00Blade

front_end/models/ai_assistance/ExtensionScope.test.ts

@@ -102,6 +102,20 @@ describe('ExtensionScope', () => {
       const selector = ExtensionScope.ExtensionScope.getSelectorForNode(node);
       assert.strictEqual(selector, '.my\\.special-class.my-class-b');
     });
+
+    it('should work with only ai generated class', () => {
+      const node = createNode({
+        getAttribute: attribute => {
+          if (attribute === 'class') {
+            return `${Injected.AI_ASSISTANCE_CSS_CLASS_NAME}-2`;
+          }
+
+          return undefined;
+        }
+      });
+      const selector = ExtensionScope.ExtensionScope.getSelectorForNode(node);
+      assert.strictEqual(selector, 'div');
+    });
   });
 
   describe('getSelectorFromRules', () => {

front_end/models/ai_assistance/ExtensionScope.ts

@@ -219,12 +219,20 @@ export class ExtensionScope {
   }
 
   static getSelectorForNode(node: SDK.DOMModel.DOMNode): string {
-    return node.simpleSelector()
-        .split('.')
-        .filter(chunk => {
-          return !chunk.startsWith(AI_ASSISTANCE_CSS_CLASS_NAME);
-        })
-        .join('.');
+    const simpleSelector = node.simpleSelector()
+                               .split('.')
+                               .filter(chunk => {
+                                 return !chunk.startsWith(AI_ASSISTANCE_CSS_CLASS_NAME);
+                               })
+                               .join('.');
+    // Handle the edge case where the node is DIV and the
+    // only selector is the AI_ASSISTANCE_CSS_CLASS_NAME
+    if (simpleSelector) {
+      return simpleSelector;
+    }
+
+    // Fallback to the HTML tag
+    return node.localName() || node.nodeName().toLowerCase();
   }
 
   static getSourceLocation(styleRule: SDK.CSSRule.CSSStyleRule): string|undefined {