Bug 795307 - Use telemetry to report touch enabled device stats. r=nfroyd

toolkit/components/telemetry/Histograms.json

@@ -2260,5 +2260,10 @@
   "READ_SAVED_PING_SUCCESS": {
     "kind": "boolean",
     "description": "Sucessful reading a saved ping file"
+  },
+  "TOUCH_ENABLED_DEVICE": {
+    "kind": "boolean",
+    "description": "The device supports touch input",
+    "cpp_guard": "XP_WIN"
   }
 }

widget/windows/nsLookAndFeel.cpp

@@ -12,6 +12,7 @@
 #include "nsUXThemeConstants.h"
 #include "gfxFont.h"
 #include "WinUtils.h"
+#include "mozilla/Telemetry.h"
 
 using namespace mozilla::widget;
 using mozilla::LookAndFeel;
@@ -38,8 +39,18 @@ static int32_t GetSystemParam(long flag, int32_t def)
     return ::SystemParametersInfo(flag, 0, &value, 0) ? value : def;
 }
 
+static int32_t IsTouchPresent()
+{
+  int32_t touchCapabilities;
+  touchCapabilities = ::GetSystemMetrics(SM_DIGITIZER);
+  return ((touchCapabilities & NID_READY) && 
+          (touchCapabilities & (NID_EXTERNAL_TOUCH | NID_INTEGRATED_TOUCH)));
+}
+
 nsLookAndFeel::nsLookAndFeel() : nsXPLookAndFeel()
 {
+  mozilla::Telemetry::Accumulate(mozilla::Telemetry::TOUCH_ENABLED_DEVICE,
+                                 IsTouchPresent());
 }
 
 nsLookAndFeel::~nsLookAndFeel()
@@ -365,13 +376,7 @@ nsLookAndFeel::GetIntImpl(IntID aID, int32_t &aResult)
         aResult = !IsAppThemed();
         break;
     case eIntID_TouchEnabled:
-        aResult = 0;
-        int32_t touchCapabilities;
-        touchCapabilities = ::GetSystemMetrics(SM_DIGITIZER);
-        if ((touchCapabilities & NID_READY) && 
-           (touchCapabilities & (NID_EXTERNAL_TOUCH | NID_INTEGRATED_TOUCH))) {
-            aResult = 1;
-        }
+        aResult = IsTouchPresent();
         break;
     case eIntID_WindowsDefaultTheme:
         aResult = nsUXThemeData::IsDefaultWindowTheme();