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/verttext.cpp b/gm/verttext.cpp
index 37cf37c..700fb25 100644
--- a/gm/verttext.cpp
+++ b/gm/verttext.cpp
@@ -13,17 +13,17 @@
 namespace skiagm {
 
 #define TEXT_SIZE   48
-static const char gText[] = "Hello";
+constexpr char gText[] = "Hello";
 
 //Before shaping
-//static const char gText[] = "「テスト。」";
-//static const char gText[] = {0xE3,0x80,0x8C, 0xE3,0x83,0x86, 0xE3,0x82,0xB9, 0xE3,0x83,0x88, 0xE3,0x80,0x82, 0xE3,0x80,0x8D, 0x0};
+//constexpr char gText[] = "「テスト。」";
+//constexpr char gText[] = {0xE3,0x80,0x8C, 0xE3,0x83,0x86, 0xE3,0x82,0xB9, 0xE3,0x83,0x88, 0xE3,0x80,0x82, 0xE3,0x80,0x8D, 0x0};
 
 //After shaping
-//static const char gText[] = "﹁テスト︒﹂";
-//static const char gText[] = {0xEF,0xB9,0x81, 0xE3,0x83,0x86, 0xE3,0x82,0xB9, 0xE3,0x83,0x88, 0xEF,0xB8,0x92, 0xEF,0xB9,0x82, 0x0};
+//constexpr char gText[] = "﹁テスト︒﹂";
+//constexpr char gText[] = {0xEF,0xB9,0x81, 0xE3,0x83,0x86, 0xE3,0x82,0xB9, 0xE3,0x83,0x88, 0xEF,0xB8,0x92, 0xEF,0xB9,0x82, 0x0};
 
-static const size_t gLen = sizeof(gText) - sizeof(gText[0]);
+constexpr size_t gLen = sizeof(gText) - sizeof(gText[0]);
 
 class VertTextGM : public GM {
 public: