use the actual line contents when processing physical lines

src/flake8/checker.py

@@ -581,7 +581,7 @@ class FileChecker:
             line_no = token[2][0]
             with self.processor.inside_multiline(line_number=line_no):
                 for line in self.processor.split_line(token):
-                    self.run_physical_checks(line + "\n")
+                    self.run_physical_checks(line)
 
 
 def _pool_init() -> None:

src/flake8/processor.py

@@ -233,8 +233,10 @@ class FileProcessor:
 
         This also auto-increments the line number for the caller.
         """
-        for line in token[1].split("\n")[:-1]:
-            yield line
+        # intentionally don't include the last line, that line will be
+        # terminated later by a future end-of-line
+        for line_no in range(token.start[0], token.end[0]):
+            yield self.lines[line_no - 1]
             self.line_number += 1
 
     def keyword_arguments_for(