move parts of SkPoint to SkPointPriv

Move specialized SkPoint methods to SkPointPriv.
Use constexpr and inline initialization where possible.

R=reed@google.com,bsalomon@google.com
Bug: skia: 6898
Change-Id: I01ec5186f010f2dc80c068c70d9cc352f3221338
Reviewed-on: https://skia-review.googlesource.com/68700
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Ravi Mistry <rmistry@google.com>
diff --git a/tests/GeometryTest.cpp b/tests/GeometryTest.cpp
index ad3a6b4..a926501 100644
--- a/tests/GeometryTest.cpp
+++ b/tests/GeometryTest.cpp
@@ -6,8 +6,9 @@
  */
 
 #include "SkGeometry.h"
-#include "Test.h"
+#include "SkPointPriv.h"
 #include "SkRandom.h"
+#include "Test.h"
 #include <array>
 
 static bool nearly_equal(const SkPoint& a, const SkPoint& b) {
@@ -152,7 +153,7 @@
     const int qcount = quadder.countQuads();
     const int pcount = qcount * 2 + 1;
 
-    REPORTER_ASSERT(r, SkPointsAreFinite(qpts, pcount));
+    REPORTER_ASSERT(r, SkPointPriv::AreFinite(qpts, pcount));
 }
 
 /**