[Symsrc] - Add OWNERS and update the README

Bug: 1008864
Change-Id: I992c7e31e4d31c0e815af6ec64812e7a76c2f1c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1832721
Auto-Submit: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Bruce Dawson <brucedawson@chromium.org>
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703424}

tools/symsrc/OWNERS

+brucedawson@chromium.org
+sebmarchand@chromium.org

tools/symsrc/README.chromium

 These files are related to the symbol and source server.
 
-This requires some Microsoft utilities.  From a 32-bit WinDbg installation with
-source server support, copy the following files to this directory:
-  dbghelp.dll
-  pdbstr.exe
-  srctool.exe
-
 The follow files were copied from the BSD licensed pefile-1.2.9.1:
   COPYING-pefile
   pefile.py
 
 pefile is available from:
-  http://code.google.com/p/pefile/
+  https://github.com/erocarrera/pefile