[Logging] Make /var/log/chrome/chrome relative

This is more convenient for downloaded log archives.

Bug: 976821
Change-Id: If9c65729fa7f20dd080bbde5aa3873bcfbac7a22
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1671527Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Vladislav Kuzkokov <vkuzkokov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672545}

chrome/common/logging_chrome.cc

@@ -212,9 +212,10 @@ base::FilePath SetUpSymlinkIfNeeded(const base::FilePath& symlink_path,
     }
   }
   // If all went well, the symlink no longer exists.  Recreate it.
-  if (!base::CreateSymbolicLink(target_path, symlink_path)) {
+  base::FilePath relative_target_path = target_path.BaseName();
+  if (!base::CreateSymbolicLink(relative_target_path, symlink_path)) {
     DPLOG(ERROR) << "Unable to create symlink " << symlink_path.value()
-                 << " pointing at " << target_path.value();
+                 << " pointing at " << relative_target_path.value();
   }
   return target_path;
 }