Add cross-platform API to get the form factor of the device

chrome/chrome_common.gypi

Index: chrome/chrome_common.gypi
diff --git a/chrome/chrome_common.gypi b/chrome/chrome_common.gypi
index 47750689bb675f91a14163a7444fe74b911d2770..f8e4c549dcd242df35c46793bfb04778f1c02571 100644
--- a/chrome/chrome_common.gypi
+++ b/chrome/chrome_common.gypi
@@ -289,6 +289,10 @@
         'common/favicon/favicon_types.h',
         'common/favicon/favicon_url_parser.cc',
         'common/favicon/favicon_url_parser.h',
+        'common/form_factor_android.cc',
+        'common/form_factor_desktop.cc',

[Alexei Svitkine (slow), 2013/10/29 15:26:21]

I think we don't have gypi magic for _desktop.cc files, so you'll need to
manually exclude those from the non-ios, non-android build.

See how we do it here using the "sources!" directive:

https://code.google.com/p/chromium/codesearch#chromium/src/chrome/chrome_brow...

(Add the same sort of thing to this file.)

[yao, 2013/10/29 19:21:57]

Done.

+        'common/form_factor_ios.mm',
+        'common/form_factor.h',
         'common/icon_with_badge_image_source.cc',
         'common/icon_with_badge_image_source.h',
         'common/importer/firefox_importer_utils.cc',