Add chrome_proxy.exe target on Windows

This change adds a new executable to Windows called chrome_proxy.exe which
opens chrome.exe with all arguments forwarded.

In a future patch bookmark app shortcuts will be updated to point to
chrome_proxy.exe instead of chrome.exe so they don't pick up the
chrome.VisualElementsManifest.xml file when pinned to the Windows 10
start menu. This fixes a bug where pinned bookmark app shortcuts all
use the Chrome logo instead of their own.

Bug: 732357
Change-Id: I551093f6f111041b424d30ec3f829fa6a06a265c
Reviewed-on: https://chromium-review.googlesource.com/c/1362695
Reviewed-by: Greg Thompson <grt@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614177}