1 files changed, 44 insertions, 2 deletions
diff --git a/dom/media/webrtc/MediaTrackConstraints.h b/dom/media/webrtc/MediaTrackConstraints.h
index 842fea0d2d..693c905d5f 100644
--- a/dom/media/webrtc/MediaTrackConstraints.h
+++ b/dom/media/webrtc/MediaTrackConstraints.h
@@ -261,8 +261,50 @@ public:
                         aOther.mMozAutoGainControl, advanced, aList) {}
 };
 
-template<> bool NormalizedConstraintSet::Range<bool>::Merge(const Range& aOther);
-template<> void NormalizedConstraintSet::Range<bool>::FinalizeMerge();
+// The Range code works surprisingly well for bool, except when averaging ideals.
+template<>
+bool
+NormalizedConstraintSet::Range<bool>::Merge(const Range& aOther) {
+  if (!Intersects(aOther)) {
+    return false;
+  }
+  Intersect(aOther);
+
+  // To avoid "unsafe use of type 'bool'", we keep counter in mMergeDenominator
+  uint32_t counter = mMergeDenominator >> 16;
+  uint32_t denominator = mMergeDenominator & 0xffff;
+
+  if (aOther.mIdeal.isSome()) {
+    if (mIdeal.isNothing()) {
+      mIdeal.emplace(aOther.Get(false));
+      counter = aOther.Get(false);
+      denominator = 1;
+    } else {
+      if (!denominator) {
+        counter = Get(false);
+        denominator = 1;
+      }
+      counter += aOther.Get(false);
+      denominator++;
+    }
+  }
+  mMergeDenominator = ((counter & 0xffff) << 16) + (denominator & 0xffff);
+  return true;
+}
+
+template<>
+void
+NormalizedConstraintSet::Range<bool>::FinalizeMerge()
+{
+  if (mMergeDenominator) {
+    uint32_t counter = mMergeDenominator >> 16;
+    uint32_t denominator = mMergeDenominator & 0xffff;
+
+    *mIdeal = !!(counter / denominator);
+    mMergeDenominator = 0;
+  }
+}
+
 
 // Used instead of MediaTrackConstraints in lower-level code.
 struct NormalizedConstraints : public NormalizedConstraintSet