Bug 1369319 - Part 1: Block device sensor events when 'privacy.resistFingerprinting' is true. r=arthuredelstein,bz

This patch adds a nsDeviceSensors::IsSensorEventBlocked() function to check
whether device sensor events should be blocked and replaces original
'device.sensors.enabled' check with this function. This function will not only
check 'privacy.resistFingerprinting' but also check 'device.sensors.enabled'.

MozReview-Commit-ID: 7NZiBHWN6y6

--HG--
extra : rebase_source : 54d4cd99e5dfb089f11b19b0b487ff5add34b69c

dom/system/nsDeviceSensors.cpp

@@ -7,6 +7,7 @@
 #include "mozilla/Hal.h"
 #include "mozilla/HalSensor.h"
 
+#include "nsContentUtils.h"
 #include "nsDeviceSensors.h"
 
 #include "nsIDOMEvent.h"
@@ -128,7 +129,7 @@ nsDeviceSensors::~nsDeviceSensors()
 
 NS_IMETHODIMP nsDeviceSensors::HasWindowListener(uint32_t aType, nsIDOMWindow *aWindow, bool *aRetVal)
 {
-  if (!mEnabled)
+  if (AreSensorEventsDisabled(aWindow))
     *aRetVal = false;
   else
     *aRetVal = mWindowListeners[aType]->IndexOf(aWindow) != NoIndex;
@@ -169,7 +170,7 @@ static bool sTestSensorEvents = false;
 
 NS_IMETHODIMP nsDeviceSensors::AddWindowListener(uint32_t aType, nsIDOMWindow *aWindow)
 {
-  if (!mEnabled)
+  if (AreSensorEventsDisabled(aWindow))
     return NS_OK;
 
   if (mWindowListeners[aType]->IndexOf(aWindow) != NoIndex)
@@ -567,3 +568,19 @@ nsDeviceSensors::FireDOMMotionEvent(nsIDOMDocument *domdoc,
   mLastAcceleration.reset();
   mLastDOMMotionEventTime = TimeStamp::Now();
 }
+
+bool
+nsDeviceSensors::AreSensorEventsDisabled(nsIDOMWindow* aWindow)
+{
+  if (!mEnabled) {
+    return true;
+  }
+
+  nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(aWindow);
+
+  if (!window) {
+    return false;
+  }
+
+  return nsContentUtils::ShouldResistFingerprinting(window->GetDocShell());
+}

dom/system/nsDeviceSensors.h

@@ -74,6 +74,8 @@ private:
     return mWindowListeners[aType]->Length() > 0;
   }
 
+  bool AreSensorEventsDisabled(nsIDOMWindow* aWindow);
+
   mozilla::TimeStamp mLastDOMMotionEventTime;
   bool mIsUserProximityNear;
   mozilla::Maybe<DeviceAccelerationInit> mLastAcceleration;