Add null check of the return value of Document::frame() in DTL::reportResponseReceived()

BUG=578849

Review URL: https://codereview.chromium.org/1603783002

(cherry picked from commit d2535dca624b5531247dbcbc2048dded6e9c45fc)

Cr-Original-Commit-Position: refs/heads/master@{#370674}
Cr-Commit-Position: refs/branch-heads/2623@{#639}
Cr-Branched-From: 92d77538a86529ca35f9220bd3cd512cbea1f086-refs/heads/master@{#369907}

1 files changed, 5 insertions, 0 deletions

diff --git a/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp b/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp
index b1a9909..72a90ad 100644
--- a/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/DocumentThreadableLoader.cpp
@@ -568,6 +568,11 @@ void DocumentThreadableLoader::handlePreflightResponse(const ResourceResponse& r
 void DocumentThreadableLoader::reportResponseReceived(unsigned long identifier, const ResourceResponse& response)
 {
     LocalFrame* frame = document().frame();
+    // We are seeing crashes caused by nullptr (crbug.com/578849). But the frame
+    // must be set here. TODO(horo): Find the root cause of the unset frame.
+    ASSERT(frame);
+    if (!frame)
+        return;
     DocumentLoader* loader = frame->loader().documentLoader();
     TRACE_EVENT_INSTANT1("devtools.timeline", "ResourceReceiveResponse", TRACE_EVENT_SCOPE_THREAD, "data", InspectorReceiveResponseEvent::data(identifier, frame, response));
     InspectorInstrumentation::didReceiveResourceResponse(frame, identifier, loader, response, resource() ? resource()->loader() : 0);