Fix dangling raw_ptr errors and related issues (see #3239)

- Use raw_ptr in class container fields.
- Use defined lifespan for StreamReaderURLLoader.
- Fix lifespan assumptions for WebContents/RFH usage.

libcef/browser/views/widget_impl.h

@@ -89,7 +89,7 @@ class CefWidgetImpl : public views::Widget,
   bool initialized_ = false;
 
   // Map of Profile* to count.
-  using ProfileMap = std::map<Profile*, size_t>;
+  using ProfileMap = std::map<raw_ptr<Profile>, size_t>;
   ProfileMap associated_profiles_;
 
   CefColorProviderTracker color_provider_tracker_{this};