Enable "Find in selection" within single lines

Fixes (or implements? ;) ) Microsoft/issues#15125

src/vs/editor/contrib/find/browser/findWidget.ts

@@ -276,14 +276,14 @@ export class FindWidget extends Widget implements IOverlayWidget {
 
 	/**
 	 * If 'selection find' is ON we should not disable the button (its function is to cancel 'selection find').
-	 * If 'selection find' is OFF we enable the button only if there is a multi line selection.
+	 * If 'selection find' is OFF we enable the button only if there is a selection.
 	 */
 	private _updateToggleSelectionFindButton(): void {
 		let selection = this._codeEditor.getSelection();
-		let isMultiLineSelection = selection ? (selection.startLineNumber !== selection.endLineNumber) : false;
+		let isSelection = selection ? (selection.startLineNumber !== selection.endLineNumber || selection.startColumn !== selection.endColumn) : false;
 		let isChecked = this._toggleSelectionFind.checked;
 
-		this._toggleSelectionFind.setEnabled(this._isVisible && (isChecked || isMultiLineSelection));
+		this._toggleSelectionFind.setEnabled(this._isVisible && (isChecked || isSelection));
 	}
 
 	private _updateButtons(): void {