Add a comment on PRODUCT_STRING_PATH usage in chrome_elf.

chrome_elf/chrome_elf_constants.cc

Index: chrome_elf/chrome_elf_constants.cc
diff --git a/chrome_elf/chrome_elf_constants.cc b/chrome_elf/chrome_elf_constants.cc
index 2182268a0cfec8f074af106f261c6942f2a36fa8..b9fb5de0ebded145ec3667c96993b8beebd059d4 100644
--- a/chrome_elf/chrome_elf_constants.cc
+++ b/chrome_elf/chrome_elf_constants.cc
@@ -5,6 +5,9 @@
 #include "chrome_elf/chrome_elf_constants.h"
 
 #if defined(GOOGLE_CHROME_BUILD)
+// Using PRODUCT_STRING_PATH is wrong as it makes Google Chrome and Canary

[robertshield, 2016/01/25 22:21:03]

Suggest "Using PRODUCT_STRING_PATH will make Google Chrome and Canary
configurations collide. This was deemed to be the best option due to ELF's
inability to depend on BrowserDistribution. http://crbug.com/577820".

It's only wrong if there's a better overall option, which it doesn't look like
there is in this case.

[gab, 2016/01/26 02:14:55]

Done.
The "better" option is to turn the portion of installer_util which is not chrome
specific into a component, but that is far from done, so yea no clean short term
solution (short of duplicating more code to figure out SxS in ELF).

Given I assume the BL's config is fairly stable and would only be used to
rollback all channels in case of emergency it's probably okay.

+// configurations collide but this was still deemed the best option for Chrome
+// ELF per inability to depend on BrowserDistribution. http://crbug.com/577820
 #define PRODUCT_STRING_PATH L"Google\\Chrome"
 #elif defined(CHROMIUM_BUILD)
 #define PRODUCT_STRING_PATH L"Chromium"