Fix nullptr deref in maybeRenderFallbackContent()

third_party/WebKit/public/web/WebLocalFrame.h

Index: third_party/WebKit/public/web/WebLocalFrame.h
diff --git a/third_party/WebKit/public/web/WebLocalFrame.h b/third_party/WebKit/public/web/WebLocalFrame.h
index 5242affddc5bbb0181c92b587b46240297465f3b..710a6e3dff20a9b39e6bb1a988f2aa1ee5f37e6e 100644
--- a/third_party/WebKit/public/web/WebLocalFrame.h
+++ b/third_party/WebKit/public/web/WebLocalFrame.h
@@ -153,9 +153,17 @@ class WebLocalFrame : public WebFrame {
                         WebHistoryLoadType = kWebHistoryDifferentDocumentLoad,
                         bool is_client_redirect = false) = 0;
 
-  // On load failure, attempts to make frame's parent rendering fallback content
-  // and stop this frame loading.
-  virtual bool MaybeRenderFallbackContent(const WebURLError&) const = 0;
+  enum FallbackContentResult {
+    // An error page should be shown instead of fallback.
+    NoFallbackContent,
+    // Something else committed, no fallback content or error page needed.
+    NoLoadInProgress,
+    // Fallback content rendered, no error page needed.
+    FallbackRendered
+  };
+  // On load failure, attempts to make frame's parent render fallback content.
+  virtual FallbackContentResult MaybeRenderFallbackContent(
+      const WebURLError&) const = 0;
 
   // Called when a navigation is blocked because a Content Security Policy (CSP)
   // is infringed.