Record concat as Concat.

This seems to cause very slight diffs on GMs.
https://gold.skia.org/search2?issue=1462983002&unt=true&query=source_type%3Dgm&master=false

I'm not sure I understand why.
The diffs to at least pictureshader look like improvements.

BUG=skia:4584

Review URL: https://codereview.chromium.org/1462983002
diff --git a/src/core/SkRecorder.cpp b/src/core/SkRecorder.cpp
index a3c9513..d90b2c0 100644
--- a/src/core/SkRecorder.cpp
+++ b/src/core/SkRecorder.cpp
@@ -352,15 +352,10 @@
 }
 
 void SkRecorder::didConcat(const SkMatrix& matrix) {
-    this->didSetMatrix(this->getTotalMatrix());
+    APPEND(Concat, matrix);
 }
 
 void SkRecorder::didSetMatrix(const SkMatrix& matrix) {
-    SkDEVCODE(if (matrix != this->getTotalMatrix()) {
-        matrix.dump();
-        this->getTotalMatrix().dump();
-        SkASSERT(matrix == this->getTotalMatrix());
-    })
     APPEND(SetMatrix, matrix);
 }