DevTools: ignore provisional frames when loading cached resources

Bug: 1096278
Change-Id: I1fa22fb963cc225b95447cb9caea12f030bead90
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2324886Reviewed-by: Łukasz Anforowicz <lukasza@chromium.org>
Commit-Queue: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792779}

third_party/blink/renderer/core/inspector/inspector_resource_content_loader.cc

@@ -69,6 +69,8 @@ void InspectorResourceContentLoader::Start() {
   InspectedFrames* inspected_frames =
       MakeGarbageCollected<InspectedFrames>(inspected_frame_);
   for (LocalFrame* frame : *inspected_frames) {
+    if (!frame->Loader().StateMachine()->CommittedFirstRealDocumentLoad())
+      continue;
     documents.push_back(frame->GetDocument());
     documents.AppendVector(InspectorPageAgent::ImportsForFrame(frame));
   }