[geometry] replace m12 with m21 when transform DOMPoint from DOMMatrix.

third_party/WebKit/Source/core/geometry/DOMPointReadOnly.cpp

Index: third_party/WebKit/Source/core/geometry/DOMPointReadOnly.cpp
diff --git a/third_party/WebKit/Source/core/geometry/DOMPointReadOnly.cpp b/third_party/WebKit/Source/core/geometry/DOMPointReadOnly.cpp
index fa25625dc279fad11edf7e8150ea6c63bb80aaa3..c15c6e64a6296b3f87d852d5f3eb2cfb56ca7d29 100644
--- a/third_party/WebKit/Source/core/geometry/DOMPointReadOnly.cpp
+++ b/third_party/WebKit/Source/core/geometry/DOMPointReadOnly.cpp
@@ -42,7 +42,7 @@ DOMPoint* DOMPointReadOnly::matrixTransform(DOMMatrixInit& other,
 
   if (matrix->is2D() && z() == 0 && w() == 1) {
     double transformed_x =
-        x() * matrix->m11() + y() * matrix->m12() + matrix->m41();
+        x() * matrix->m11() + y() * matrix->m21() + matrix->m41();
     double transformed_y =
         x() * matrix->m12() + y() * matrix->m22() + matrix->m42();
     return DOMPoint::Create(transformed_x, transformed_y, 0, 1);