[DevTools] clean breakpoints and decorations onUISourceCodeContentChanged

third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js

Index: third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js
diff --git a/third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js b/third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js
index 0c827449e481f1cf49502fbd4f9c77e79043e360..d6d7b9d2cd92837f581f8aa2a41496b281970ada 100644
--- a/third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js
+++ b/third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js
@@ -185,8 +185,10 @@ Sources.JavaScriptSourceFrame = class extends Sources.UISourceCodeFrame {
    * @override
    */
   onUISourceCodeContentChanged() {
-    for (var decoration of this._breakpointDecorations)
-      decoration.breakpoint.remove();
+    for (var decoration of this._breakpointDecorations) {
+      if (decoration.breakpoint)
+        decoration.breakpoint.remove();
+    }
     super.onUISourceCodeContentChanged();
   }