Provide approximate type functions for SkMatrix44.

ui/gfx/transform.cc

Index: ui/gfx/transform.cc
diff --git a/ui/gfx/transform.cc b/ui/gfx/transform.cc
index 057c93c60b8cd2746ed7b75ab1c3d18200856c31..e129af520640f35bef1fc47718f01f4351e67e40 100644
--- a/ui/gfx/transform.cc
+++ b/ui/gfx/transform.cc
@@ -32,6 +32,14 @@ SkMScalar TanDegrees(double degrees) {
   return SkDoubleToMScalar(std::tan(radians));
 }
 
+inline bool ApproximatelyZero(SkMScalar x, SkMScalar tolerance) {
+  return std::abs(x) <= tolerance;
+}
+
+inline bool ApproximatelyOne(SkMScalar x, SkMScalar tolerance) {
+  return std::abs(x - SkDoubleToMScalar(1.0)) <= tolerance;
+}
+
 }  // namespace
 
 Transform::Transform(SkMScalar col1row1,
@@ -210,6 +218,25 @@ void Transform::ConcatTransform(const Transform& transform) {
   matrix_.postConcat(transform.matrix_);
 }
 
+bool Transform::IsApproximatelyIdentityOrTranslation(
+    SkMScalar tolerance) const {
+  DCHECK_GE(tolerance, 0);
+  return
+      ApproximatelyOne(matrix_.get(0, 0), tolerance) &&
+      ApproximatelyZero(matrix_.get(1, 0), tolerance) &&
+      ApproximatelyZero(matrix_.get(2, 0), tolerance) &&
+      matrix_.get(3, 0) == 0 &&
+      ApproximatelyZero(matrix_.get(0, 1), tolerance) &&
+      ApproximatelyOne(matrix_.get(1, 1), tolerance) &&
+      ApproximatelyZero(matrix_.get(2, 1), tolerance) &&
+      matrix_.get(3, 1) == 0 &&
+      ApproximatelyZero(matrix_.get(0, 2), tolerance) &&
+      ApproximatelyZero(matrix_.get(1, 2), tolerance) &&
+      ApproximatelyOne(matrix_.get(2, 2), tolerance) &&
+      matrix_.get(3, 2) == 0 &&
+      matrix_.get(3, 3) == 1;
+}
+
 bool Transform::IsIdentityOrIntegerTranslation() const {
   if (!IsIdentityOrTranslation())
     return false;