Run Google Chrome with flags (not from chrome://flags) There are command line flags (or "switches") that Chromium (and Chrome) accept in order to enable particular features or modify otherwise default functionality.

Chromium Command Line Switches

Run Chromium with flags

Tried Chrome 41.0.xx and Chromium 43.0.xxx shell with:

# echo "chrome &lt;flags&gt;" &gt; /data/local/tmp/android-webview-command-line
# echo "chrome &lt;flags&gt;" &gt; /data/local/tmp/content-shell-command-line
# echo "chrome --sync-url whatever" &gt; /data/local/tmp/chrome-command-line


Want to add --sync-url flag to use my sync server instead of Google sync servers. chrome://flags only enable/disable flags but wont let you add new flag. Any idea how to run Chrome with flags on Android or directly add these into default profile?
You need to add the entire command into the /data/local/tmp/chrome-command-line file. For example, I usually you want to skip the "First run experience", and I do: 

# echo "chrome --disable-fre" &gt; /data/local/tmp/chrome-command-line

You probably need

# echo "chrome --sync-url whatever" &gt; /data/local/tmp/chrome-command-line