CSS Motion Path: offset-anchor should default to auto

third_party/WebKit/Source/core/style/ComputedStyle.cpp

Index: third_party/WebKit/Source/core/style/ComputedStyle.cpp
diff --git a/third_party/WebKit/Source/core/style/ComputedStyle.cpp b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
index c6046e0a2df0537c419be32bcb9e05086d46d8a2..5906d8692a6278b1ccfa0f7b96d958e076d6dc6b 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.cpp
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
@@ -1368,6 +1368,8 @@ void ComputedStyle::applyMotionPathTransform(
   if (!motionData.m_path) {
     return;
   }
+  const LengthPoint& position = offsetPosition();
+  const LengthPoint& anchor = offsetAnchor();
   const StylePath& motionPath = *motionData.m_path;
   float pathLength = motionPath.length();
   float distance = floatValueForLength(motionData.m_distance, pathLength);
@@ -1389,9 +1391,7 @@ void ComputedStyle::applyMotionPathTransform(
 
   float originShiftX = 0;
   float originShiftY = 0;
-  if (RuntimeEnabledFeatures::cssOffsetPositionAnchorEnabled()) {
-    // TODO(ericwilligers): crbug.com/638055 Support offset-anchor: auto.
-    const LengthPoint& anchor = offsetAnchor();
+  if (position.x() != Length(Auto) || anchor.x() != Length(Auto)) {

[sashab, 2016/12/12 01:11:26]

You removed a runtime enabled feature flag? Please add that to the CL
description.

Also is this if statement needed? I feel like the originShift code should apply
and work and handle the Auto case. Maybe I'm misunderstanding what this is for;
if so, a comment is needed.

[Eric Willigers, 2016/12/12 01:57:14]

comments added

     originShiftX = floatValueForLength(anchor.x(), boundingBox.width()) -
                    floatValueForLength(transformOriginX(), boundingBox.width());
     originShiftY =
@@ -1403,9 +1403,8 @@ void ComputedStyle::applyMotionPathTransform(
                       point.y() - originY + originShiftY);
   transform.rotate(angle + motionData.m_rotation.angle);
 
-  if (RuntimeEnabledFeatures::cssOffsetPositionAnchorEnabled()) {
+  if (position.x() != Length(Auto) || anchor.x() != Length(Auto))

[sashab, 2016/12/12 01:11:26]

Why only x() and not y()?

[Eric Willigers, 2016/12/12 01:57:14]

position and anchor are 
<position> | auto
i.e. either a pair of positions, or auto.

Checking y would be redundant.

     transform.translate(-originShiftX, -originShiftY);
-  }
 }
 
 void ComputedStyle::setTextShadow(PassRefPtr<ShadowList> s) {