Replace a lot of 'static const' with 'constexpr' or 'const'.

'static const' means, there must be at most one of these, and initialize it at
compile time if possible or runtime if necessary.  This leads to unexpected
code execution, and TSAN* will complain about races on the guard variables.

Generally 'constexpr' or 'const' are better choices.  Neither can cause races:
they're either intialized at compile time (constexpr) or intialized each time
independently (const).

This CL prefers constexpr where possible, and uses const where not.  It even
prefers constexpr over const where they don't make a difference... I want to have
lots of examples of constexpr for people to see and mimic.

The scoped-to-class static has nothing to do with any of this, and is not changed.

* Not yet on the bots, which use an older TSAN.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2300623005

Review-Url: https://codereview.chromium.org/2300623005
diff --git a/gm/smallpaths.cpp b/gm/smallpaths.cpp
index 926b2a2..ddbb60d 100644
--- a/gm/smallpaths.cpp
+++ b/gm/smallpaths.cpp
@@ -11,7 +11,7 @@
 typedef SkScalar (*MakePathProc)(SkPath*);
 
 static SkScalar make_triangle(SkPath* path) {
-    static const int gCoord[] = {
+    constexpr int gCoord[] = {
         10, 20, 15, 5, 30, 30
     };
     path->moveTo(SkIntToScalar(gCoord[0]), SkIntToScalar(gCoord[1]));
@@ -154,7 +154,7 @@
     return SkIntToScalar(70);
 }
 
-static const MakePathProc gProcs[] = {
+constexpr MakePathProc gProcs[] = {
     make_triangle,
     make_rect,
     make_oval,
@@ -167,7 +167,7 @@
     make_battery2
 };
 
-static const SkScalar gWidths[] = {
+constexpr SkScalar gWidths[] = {
     2.0f,
     3.0f,
     4.0f,
@@ -180,7 +180,7 @@
     0.0f,
 };
 
-static const SkScalar gMiters[] = {
+constexpr SkScalar gMiters[] = {
     2.0f,
     3.0f,
     3.0f,