Fix nullptr deref in maybeRenderFallbackContent()

third_party/WebKit/Source/web/tests/WebFrameTest.cpp

Index: third_party/WebKit/Source/web/tests/WebFrameTest.cpp
diff --git a/third_party/WebKit/Source/web/tests/WebFrameTest.cpp b/third_party/WebKit/Source/web/tests/WebFrameTest.cpp
index 6499c5330e00aa88c0e7cc019b5ae104eb2573ca..926d33740b7ad84e3b8c4fb0fe0e4065ade3a123 100644
--- a/third_party/WebKit/Source/web/tests/WebFrameTest.cpp
+++ b/third_party/WebKit/Source/web/tests/WebFrameTest.cpp
@@ -11588,4 +11588,66 @@ TEST_F(WebFrameTest, LocalFrameWithRemoteParentIsTransparent) {
   view->close();
 }
 
+class TestFallbackWebFrameClient : public FrameTestHelpers::TestWebFrameClient {
+ public:
+  explicit TestFallbackWebFrameClient() : m_childClient(nullptr) {}
+
+  void setChildWebFrameClient(TestFallbackWebFrameClient* client) {
+    m_childClient = client;
+  }
+
+  WebLocalFrame* createChildFrame(
+      WebLocalFrame* parent,
+      WebTreeScopeType scope,
+      const WebString&,
+      const WebString&,
+      WebSandboxFlags,
+      const WebFrameOwnerProperties& frameOwnerProperties) override {
+    DCHECK(m_childClient);
+    WebLocalFrame* frame =
+        WebLocalFrame::create(scope, m_childClient, nullptr, nullptr);
+    parent->appendChild(frame);
+    return frame;
+  }
+
+  WebNavigationPolicy decidePolicyForNavigation(
+      const NavigationPolicyInfo& info) override {
+    if (m_childClient || KURL(info.urlRequest.url()) == blankURL())
+      return WebNavigationPolicyCurrentTab;
+    return WebNavigationPolicyHandledByClient;
+  }
+
+ private:
+  TestFallbackWebFrameClient* m_childClient;
+};
+
+TEST_F(WebFrameTest, FallbackForNonexistentProvisionalNavigation) {
+  registerMockedHttpURLLoad("fallback.html");
+  TestFallbackWebFrameClient mainClient;
+  TestFallbackWebFrameClient childClient;
+  mainClient.setChildWebFrameClient(&childClient);
+
+  FrameTestHelpers::WebViewHelper webViewHelper;
+  webViewHelper.initialize(true, &mainClient);
+
+  WebLocalFrameImpl* mainFrame = webViewHelper.webView()->mainFrameImpl();
+  WebURLRequest request(toKURL(m_baseURL + "fallback.html"));
+  mainFrame->loadRequest(request);
+
+  // Because the child frame will be HandledByClient, the main frame will not
+  // finish loading, so we cant use
+  // FrameTestHelpers::pumpPendingRequestsForFrameToLoad.
+  Platform::current()->getURLLoaderMockFactory()->serveAsynchronousRequests();
+
+  // Overwrite the client-handled child frame navigation with about:blank.
+  WebLocalFrame* child = mainFrame->firstChild()->toWebLocalFrame();
+  child->loadRequest(WebURLRequest(blankURL()));
+
+  // Failing the original child frame navigation and trying to render fallback
+  // content shouldn't crash. It should return true as though it showed
+  // fallback. This is so the caller won't attempt to replace the correctly
+  // empty frame with an error page.
+  EXPECT_TRUE(child->maybeRenderFallbackContent(WebURLError()));
+}
+
 }  // namespace blink