Strip path prefixes from ASan reports for isolate runs.

BUG=None
R=earthdok@chromium.org

Review URL: https://codereview.chromium.org/872353003

Cr-Commit-Position: refs/heads/master@{#315334}

tools/valgrind/asan/asan_symbolize.py

@@ -247,6 +247,9 @@ def main():
   set_symbolizer_path()
   asan_symbolize.demangle = True
   asan_symbolize.fix_filename_patterns = args.strip_path_prefix
+  # Most source paths for Chromium binaries start with
+  # /path/to/src/out/Release/../../
+  asan_symbolize.fix_filename_patterns.append('Release/../../')
   binary_name_filter = None
   if os.uname()[0] == 'Darwin':
     binary_name_filter = make_chrome_osx_binary_name_filter(