Implement unit tests and temporary MathUtil wrappers for transform functionality

ui/gfx/transform.cc

Index: ui/gfx/transform.cc
diff --git a/ui/gfx/transform.cc b/ui/gfx/transform.cc
index e1d77c343f9181d9a5ed4010ced36cfcd065d0e1..0e0bea8086b3a8034eb5de7f2811421467996037 100644
--- a/ui/gfx/transform.cc
+++ b/ui/gfx/transform.cc
@@ -116,6 +116,9 @@ void Transform::SetSkewY(double angle) {
 }
 
 void Transform::SetPerspectiveDepth(double depth) {
+  if (depth == 0)
+      return;
+
   SkMatrix44 m;
   MSET(m, 3, 2, -1.0 / depth);
   matrix_ = m;
@@ -184,6 +187,9 @@ void Transform::ConcatSkewY(double angle_y) {
 }
 
 void Transform::ConcatPerspectiveDepth(double depth) {
+  if (depth == 0)
+      return;
+
   SkMatrix44 m;
   MSET(m, 3, 2, -1.0 / depth);
   matrix_.postConcat(m);
@@ -252,6 +258,9 @@ void Transform::PreconcatSkewY(double angle_y) {
 }
 
 void Transform::PreconcatPerspectiveDepth(double depth) {
+  if (depth == 0)
+      return;
+
   SkMatrix44 m;
   MSET(m, 3, 2, -1.0 / depth);
   matrix_.preConcat(m);