Replace SkPin32 with SkTPin and remove.

SkPin32 is already just forwarding to SkTPin, so convert existing
users and remove SkPin32.

Review URL: https://codereview.chromium.org/1314583003
diff --git a/src/core/SkBitmap.cpp b/src/core/SkBitmap.cpp
index 7cc7344..7d08184 100644
--- a/src/core/SkBitmap.cpp
+++ b/src/core/SkBitmap.cpp
@@ -199,7 +199,7 @@
 
     if (pr) {
         const SkImageInfo& info = pr->info();
-        fPixelRefOrigin.set(SkPin32(dx, 0, info.width()), SkPin32(dy, 0, info.height()));
+        fPixelRefOrigin.set(SkTPin(dx, 0, info.width()), SkTPin(dy, 0, info.height()));
     } else {
         // ignore dx,dy if there is no pixelref
         fPixelRefOrigin.setZero();