Roll chromium_revision 6a04368..717238e (370362:370438) + tcmalloc

Change log: https://chromium.googlesource.com/chromium/src/+log/6a04368..717238e
Full diff: https://chromium.googlesource.com/chromium/src/+/6a04368..717238e

Also add third_party/tcmalloc to the symlink list.
As per crrev.com/1611633003 host tools require tcmalloc.
No update to Clang.

BUG=chromium:580777

Review URL: https://codereview.webrtc.org/1629373002

Cr-Commit-Position: refs/heads/master@{#11369}
diff --git a/setup_links.py b/setup_links.py
index dc93064..450def9 100755
--- a/setup_links.py
+++ b/setup_links.py
@@ -99,6 +99,7 @@
     'third_party/modp_b64',
     'third_party/requests',
     'third_party/robolectric',
+    'third_party/tcmalloc',
     'tools/android',
     'tools/grit',
     'tools/telemetry',