Add localToAbsoluteTransform and localToAncestorTransform.

third_party/WebKit/Source/platform/geometry/TransformState.cpp

Index: third_party/WebKit/Source/platform/geometry/TransformState.cpp
diff --git a/third_party/WebKit/Source/platform/geometry/TransformState.cpp b/third_party/WebKit/Source/platform/geometry/TransformState.cpp
index 9ec2073661391dd75f49b5aa40f7459213729c7b..9a35f7ebae253d6ab9930d0395596f7ea0b822b3 100644
--- a/third_party/WebKit/Source/platform/geometry/TransformState.cpp
+++ b/third_party/WebKit/Source/platform/geometry/TransformState.cpp
@@ -39,6 +39,7 @@ TransformState& TransformState::operator=(const TransformState& other)
     if (m_mapQuad)
         m_lastPlanarQuad = other.m_lastPlanarQuad;
     m_accumulatingTransform = other.m_accumulatingTransform;
+    m_forceAccumulatingTransform = other.m_forceAccumulatingTransform;
     m_direction = other.m_direction;
 
     m_accumulatedTransform.clear();
@@ -68,6 +69,9 @@ void TransformState::translateMappedCoordinates(const LayoutSize& offset)
 
 void TransformState::move(const LayoutSize& offset, TransformAccumulation accumulate)
 {
+    if (m_forceAccumulatingTransform)
+        accumulate = AccumulateTransform;
+
     if (accumulate == FlattenTransform || !m_accumulatedTransform) {
         m_accumulatedOffset += offset;
     } else {
@@ -108,6 +112,9 @@ void TransformState::applyTransform(const TransformationMatrix& transformFromCon
     if (wasClamped)
         *wasClamped = false;
 
+    if (m_forceAccumulatingTransform)

[chrishtr, 2016/03/10 16:53:39]

I don't think this works in the case of a flattening transform. The
correct transformation matrix should be the transform matrix of the
element, multiplied by a flattening transform matrix. I think this amounts to
applying the same logic as in gfx::Transform::FlattenTo2d().

[dmazzoni, 2016/03/14 20:10:37]

Good catch. Fixed this and added a new test.

+        accumulate = AccumulateTransform;
+
     if (transformFromContainer.isIntegerTranslation()) {
         move(LayoutSize(LayoutUnit(transformFromContainer.e()), LayoutUnit(transformFromContainer.f())), accumulate);
         return;
@@ -135,6 +142,7 @@ void TransformState::applyTransform(const TransformationMatrix& transformFromCon
 
 void TransformState::flatten(bool* wasClamped)
 {
+    ASSERT(!m_forceAccumulatingTransform);
     if (wasClamped)
         *wasClamped = false;
 
@@ -180,6 +188,12 @@ FloatQuad TransformState::mappedQuad(bool* wasClamped) const
     return m_accumulatedTransform->inverse().projectQuad(quad, wasClamped);
 }
 
+const TransformationMatrix& TransformState::accumulatedTransform() const
+{
+    ASSERT(m_forceAccumulatingTransform && m_accumulatingTransform);
+    return *m_accumulatedTransform;
+}
+
 void TransformState::flattenWithTransform(const TransformationMatrix& t, bool* wasClamped)
 {
     if (m_direction == ApplyTransformDirection) {