Bug 1353208 - Factor out nsSMILCompositor::GetCSSPropertyToAnimate helper method; r=dholbert

In bug 1315874 we will create a method to check if we're likely to need to
resolve base styles or not, and for that we need to extract the check for
whether or not we're animating a CSS property.

MozReview-Commit-ID: 9Ybsi91fro8

--HG--
extra : rebase_source : e2f72a7d807bfbe026fbd1a603cd993c3d502584

dom/smil/nsSMILCompositor.cpp

@@ -127,11 +127,28 @@ nsSMILCompositor::ClearAnimationEffects()
 // --------------------------
 UniquePtr<nsISMILAttr>
 nsSMILCompositor::CreateSMILAttr()
+{
+  nsCSSPropertyID propID = GetCSSPropertyToAnimate();
+
+  if (propID != eCSSProperty_UNKNOWN) {
+    return MakeUnique<nsSMILCSSProperty>(propID, mKey.mElement.get());
+  }
+
+  return mKey.mElement->GetAnimatedAttr(mKey.mAttributeNamespaceID,
+                                        mKey.mAttributeName);
+}
+
+nsCSSPropertyID
+nsSMILCompositor::GetCSSPropertyToAnimate() const
 {
   nsCSSPropertyID propID =
     nsCSSProps::LookupProperty(nsDependentAtomString(mKey.mAttributeName),
                                CSSEnabledState::eForAllContent);
-  if (nsSMILCSSProperty::IsPropertyAnimatable(propID)) {
+
+  if (!nsSMILCSSProperty::IsPropertyAnimatable(propID)) {
+    return eCSSProperty_UNKNOWN;
+  }
+
   // If we are animating the 'width' or 'height' of an outer SVG
   // element we should animate it as a CSS property, but for other elements
   // (e.g. <rect>) we should animate it as a length attribute.
@@ -141,13 +158,8 @@ nsSMILCompositor::CreateSMILAttr()
                         mKey.mAttributeName == nsGkAtoms::height) &&
                        mKey.mElement->GetNameSpaceID() == kNameSpaceID_SVG &&
                        !mKey.mElement->IsAttributeMapped(mKey.mAttributeName);
-    if (!animateAsAttr) {
-      return MakeUnique<nsSMILCSSProperty>(propID, mKey.mElement.get());
-    }
-  }
 
-  return mKey.mElement->GetAnimatedAttr(mKey.mAttributeNamespaceID,
-                                        mKey.mAttributeName);
+  return animateAsAttr ? eCSSProperty_UNKNOWN : propID;
 }
 
 uint32_t

dom/smil/nsSMILCompositor.h

@@ -76,6 +76,10 @@ public:
   // Create a nsISMILAttr for my target, on the heap.
   mozilla::UniquePtr<nsISMILAttr> CreateSMILAttr();
 
+  // Returns the CSS property this compositor should animate, or
+  // eCSSProperty_UNKNOWN if this compositor does not animate a CSS property.
+  nsCSSPropertyID GetCSSPropertyToAnimate() const;
+
   // Finds the index of the first function that will affect our animation
   // sandwich. Also toggles the 'mForceCompositing' flag if it finds that any
   // (used) functions have changed.