Bug 1160819 - ResponsiveImageSelector - improve some over-aggressive assertions

dom/base/ResponsiveImageSelector.cpp

@@ -703,8 +703,8 @@ ResponsiveImageCandidate::Density(int32_t aMatchingWidth) const
   if (mType == eCandidateType_Density) {
     return mValue.mDensity;
   } else if (mType == eCandidateType_ComputedFromWidth) {
-    if (aMatchingWidth <= 0) {
-      MOZ_ASSERT(false, "0 or negative matching width is invalid per spec");
+    if (aMatchingWidth < 0) {
+      MOZ_ASSERT(false, "Don't expect to have a negative matching width at this point");
       return 1.0;
     }
     double density = double(mValue.mWidth) / double(aMatchingWidth);

dom/html/HTMLImageElement.cpp

@@ -754,7 +754,7 @@ HTMLImageElement::NaturalHeight()
 
   if (mResponsiveSelector) {
     double density = mResponsiveSelector->GetSelectedImageDensity();
-    MOZ_ASSERT(IsFinite(density) && density > 0.0);
+    MOZ_ASSERT(density >= 0.0);
     height = NSToIntRound(double(height) / density);
     height = std::max(height, 0u);
   }
@@ -782,7 +782,7 @@ HTMLImageElement::NaturalWidth()
 
   if (mResponsiveSelector) {
     double density = mResponsiveSelector->GetSelectedImageDensity();
-    MOZ_ASSERT(IsFinite(density) && density > 0.0);
+    MOZ_ASSERT(density >= 0.0);
     width = NSToIntRound(double(width) / density);
     width = std::max(width, 0u);
   }