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

chrome/browser/web_resource/notification_promo.cc

Index: chrome/browser/web_resource/notification_promo.cc
diff --git a/chrome/browser/web_resource/notification_promo.cc b/chrome/browser/web_resource/notification_promo.cc
index 101643f7817cdee1906bcc8cd6bcee0746b4dc10..e2c7cb5821e7fa99f2c4e77f87fe5a8a5ccad313 100644
--- a/chrome/browser/web_resource/notification_promo.cc
+++ b/chrome/browser/web_resource/notification_promo.cc
@@ -24,13 +24,9 @@
 #include "components/user_prefs/pref_registry_syncable.h"
 #include "content/public/browser/user_metrics.h"
 #include "net/base/url_util.h"
+#include "ui/base/device_form_factor.h"
 #include "url/gurl.h"
 
-#if defined(OS_ANDROID)
-#include "base/command_line.h"
-#include "chrome/common/chrome_switches.h"
-#endif  // defined(OS_ANDROID)
-
 using content::UserMetricsAction;
 
 namespace {
@@ -62,9 +58,9 @@ std::string PlatformString() {
 #if defined(OS_WIN)
   return "win";
 #elif defined(OS_IOS)
-  // TODO(noyau): add iOS-specific implementation
-  const bool isTablet = false;
-  return std::string("ios-") + (isTablet ? "tablet" : "phone");
+  ui::DeviceFormFactor form_factor = ui::GetDeviceFormFactor();
+  return std::string("ios-") +
+      (form_factor == ui::DEVICE_FORM_FACTOR_TABLET ? "tablet" : "phone");
 #elif defined(OS_MACOSX)
   return "mac";
 #elif defined(OS_CHROMEOS)
@@ -72,9 +68,9 @@ std::string PlatformString() {
 #elif defined(OS_LINUX)
   return "linux";
 #elif defined(OS_ANDROID)

[Alexei Svitkine (slow), 2013/11/04 16:08:51]

Can you move this block next to OS_IOS (how about before it)?

It occurred to me that if android builds also define OS_LINUX, then this block
never gets hit. (Maybe they don't so it's correct, but better to just move this
block to be sure. Also, having it next to the iOS block makes it easier to see
that they have the same logic.)

[yao, 2013/11/04 19:38:29]

Done.

-  const bool isTablet =
-      CommandLine::ForCurrentProcess()->HasSwitch(switches::kTabletUI);
-  return std::string("android-") + (isTablet ? "tablet" : "phone");
+  ui::DeviceFormFactor form_factor = ui::GetDeviceFormFactor();
+  return (std::string("android-") +

[Alexei Svitkine (slow), 2013/11/04 16:08:51]

Nit: remove ( before std::string (and at the end), so that it's consistent with
iOS case above.

[yao, 2013/11/04 19:38:29]

Done.

+      (form_factor == ui::DEVICE_FORM_FACTOR_TABLET ? "tablet" : "phone"));
 #else
   return "none";
 #endif