Bug 1292001 - Drop TransitionProperty() and ToValue() from ElementPro…

…pertyTransition; r=boris

These are no longer needed and they make assumptions about the shape of the
keyframes/properties which are not valid if the keyframes are replaced.

Differential Revision: https://phabricator.services.mozilla.com/D64520

--HG--
extra : moz-landing-system : lando

layout/style/nsTransitionManager.cpp

@@ -356,11 +356,18 @@ void CSSTransition::UpdateStartValueFromReplacedTransition() {
 void CSSTransition::SetEffectFromStyle(dom::AnimationEffect* aEffect) {
   Animation::SetEffectNoUpdate(aEffect);
 
-  // Initialize transition property.
-  ElementPropertyTransition* pt = aEffect ? aEffect->AsTransition() : nullptr;
-  if (eCSSProperty_UNKNOWN == mTransitionProperty && pt) {
-    mTransitionProperty = pt->TransitionProperty();
-    mTransitionToValue = pt->ToValue();
+  // Initialize transition property and to value.
+  //
+  // Typically this should only be called with a KeyframeEffect representing
+  // a simple transition, but just to be sure we check the effect has the
+  // expected shape first.
+  const KeyframeEffect* keyframeEffect = aEffect->AsKeyframeEffect();
+  if (MOZ_LIKELY(keyframeEffect && keyframeEffect->Properties().Length() == 1 &&
+                 keyframeEffect->Properties()[0].mSegments.Length() == 1)) {
+    mTransitionProperty = keyframeEffect->Properties()[0].mProperty;
+    mTransitionToValue = keyframeEffect->Properties()[0].mSegments[0].mToValue;
+  } else {
+    MOZ_ASSERT_UNREACHABLE("Transition effect has unexpected shape");
   }
 }
 
@@ -768,7 +775,7 @@ bool nsTransitionManager::ConsiderInitiatingTransition(
 
     duration *= valuePortion;
 
-    startForReversingTest = oldPT->ToValue();
+    startForReversingTest = oldTransition->ToValue();
     reversePortion = valuePortion;
   }
 

layout/style/nsTransitionManager.h

@@ -50,28 +50,6 @@ struct ElementPropertyTransition : public dom::KeyframeEffect {
     return this;
   }
 
-  nsCSSPropertyID TransitionProperty() const {
-    MOZ_ASSERT(mKeyframes.Length() == 2,
-               "Transitions should have exactly two animation keyframes. "
-               "Perhaps we are using an un-initialized transition?");
-    MOZ_ASSERT(mKeyframes[0].mPropertyValues.Length() == 1,
-               "Transitions should have exactly one property in their first "
-               "frame");
-    return mKeyframes[0].mPropertyValues[0].mProperty;
-  }
-
-  AnimationValue ToValue() const {
-    // If we failed to generate properties from the transition frames,
-    // return a null value but also show a warning since we should be
-    // detecting that kind of situation in advance and not generating a
-    // transition in the first place.
-    if (mProperties.Length() < 1 || mProperties[0].mSegments.Length() < 1) {
-      NS_WARNING("Failed to generate transition property values");
-      return AnimationValue();
-    }
-    return mProperties[0].mSegments[0].mToValue;
-  }
-
   // This is the start value to be used for a check for whether a
   // transition is being reversed.  Normally the same as
   // mProperties[0].mSegments[0].mFromValue, except when this transition