Only use navigation SourceLocation when no local available

We should not replace source location with good stack trace
and line number with a poor one coming from document loader.

This is currently not an issue, but synchronous navigation
commits will have a better location because there is JavaScript
on the stack, and existing solution will ignore it.

Bug: 855189
Change-Id: Ic40b307e206a87849dc7cc3a83dde878ec948dbb
Reviewed-on: https://chromium-review.googlesource.com/c/1395140
Reviewed-by: Joel Einbinder <einbinder@chromium.org>
Commit-Queue: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619846}
1 file changed