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/samplecode/SampleFatBits.cpp b/samplecode/SampleFatBits.cpp
index 80f656e..723dca8 100644
--- a/samplecode/SampleFatBits.cpp
+++ b/samplecode/SampleFatBits.cpp
@@ -10,6 +10,7 @@
 #include "SkView.h"
 #include "SkCanvas.h"
 #include "SkPath.h"
+#include "SkPointPriv.h"
 #include "SkRegion.h"
 #include "SkShader.h"
 #include "SkUtils.h"
@@ -483,7 +484,7 @@
         SkScalar tol = 12;
 
         for (int i = 0; i < count; ++i) {
-            if (fPts[i].equalsWithinTolerance(pt, tol)) {
+            if (SkPointPriv::EqualsWithinTolerance(fPts[i], pt, tol)) {
                 index = i;
                 break;
             }