Moar comments

Source/core/animation/InvalidatableStyleInterpolation.cpp

Index: Source/core/animation/InvalidatableStyleInterpolation.cpp
diff --git a/Source/core/animation/InvalidatableStyleInterpolation.cpp b/Source/core/animation/InvalidatableStyleInterpolation.cpp
index 1de10b401231bfa59ee073ddfefec095dfb23b22..49dc3a5b1082250960c512ed59d478f177fbca37 100644
--- a/Source/core/animation/InvalidatableStyleInterpolation.cpp
+++ b/Source/core/animation/InvalidatableStyleInterpolation.cpp
@@ -128,12 +128,14 @@ void InvalidatableStyleInterpolation::applyStack(const ActiveInterpolations& int
     while (startingIndex > 0 && toInvalidatableStyleInterpolation(*interpolations.at(startingIndex)).dependsOnUnderlyingValue())
         startingIndex--;
 
+    // Compute the underlying value to composite onto.
     OwnPtr<InterpolationValue> underlyingValueOwner = nullptr;
     InterpolationValue* underlyingValue = nullptr;
-    bool shouldApply = false;
-
     const InvalidatableStyleInterpolation& firstInterpolation = toInvalidatableStyleInterpolation(*interpolations.at(startingIndex));
-    if (!firstInterpolation.dependsOnUnderlyingValue()) {
+    if (firstInterpolation.dependsOnUnderlyingValue()) {
+        underlyingValueOwner = firstInterpolation.maybeConvertUnderlyingValue(state);
+        underlyingValue = underlyingValueOwner.get();
+    } else {
         firstInterpolation.ensureValidInterpolation(state, nullptr);
         // Fast path for replace interpolations that are the last to apply.
         if (startingIndex == interpolations.size() - 1) {
@@ -148,11 +150,8 @@ void InvalidatableStyleInterpolation::applyStack(const ActiveInterpolations& int
         startingIndex++;
     }
 
-    if (!underlyingValue && startingIndex < interpolations.size()) {
-        underlyingValueOwner = toInvalidatableStyleInterpolation(*interpolations.at(startingIndex)).maybeConvertUnderlyingValue(state);
-        underlyingValue = underlyingValueOwner.get();
-    }
-
+    // Composite interpolations onto the underlying value.
+    bool shouldApply = false;
     for (size_t i = startingIndex; i < interpolations.size(); i++) {
         const InvalidatableStyleInterpolation& currentInterpolation = toInvalidatableStyleInterpolation(*interpolations.at(i));
         ASSERT(currentInterpolation.dependsOnUnderlyingValue());
@@ -179,6 +178,7 @@ void InvalidatableStyleInterpolation::applyStack(const ActiveInterpolations& int
             underlyingValue->interpolableValue().scaleAndAdd(underlyingFraction, currentInterpolation.m_cachedValue->interpolableValue());
         }
     }
+
     if (shouldApply && underlyingValue) {
         underlyingValue->type().apply(underlyingValue->interpolableValue(), underlyingValue->nonInterpolableValue(), state);
     }