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/bigrrectaaeffect.cpp b/gm/bigrrectaaeffect.cpp
index 7f79a34..8387d5e 100644
--- a/gm/bigrrectaaeffect.cpp
+++ b/gm/bigrrectaaeffect.cpp
@@ -58,7 +58,7 @@
 
         int y = kPad;
         int x = kPad;
-        static const GrPrimitiveEdgeType kEdgeTypes[] = {
+        constexpr GrPrimitiveEdgeType kEdgeTypes[] = {
             kFillAA_GrProcessorEdgeType,
             kInverseFillAA_GrProcessorEdgeType,
         };
@@ -98,9 +98,9 @@
 
 private:
     // pad between test cases
-    static const int kPad = 7;
+    static constexpr int kPad = 7;
     // gap between rect for each case that is rendered and exterior of rrect
-    static const int kGap = 3;
+    static constexpr int kGap = 3;
 
     SkRRect fRRect;
     int fWidth;
@@ -116,7 +116,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 // This value is motivated by bug chromium:477684. It has to be large to cause overflow in
 // the shader
-static const int kSize = 700;
+constexpr int kSize = 700;
 
 DEF_GM( return new BigRRectAAEffectGM (SkRRect::MakeRect(SkRect::MakeIWH(kSize, kSize)), "rect"); )
 DEF_GM( return new BigRRectAAEffectGM (SkRRect::MakeOval(SkRect::MakeIWH(kSize, kSize)), "circle"); )