change SkColorTable to be immutable

gm/tinybitmap.cpp

Index: gm/tinybitmap.cpp
diff --git a/gm/tinybitmap.cpp b/gm/tinybitmap.cpp
index 26bf25e665f6d8ed7b831b68baa64e34d6750c94..6cb9eded73944c1f7fd400ebbea9842e8755ae72 100644
--- a/gm/tinybitmap.cpp
+++ b/gm/tinybitmap.cpp
@@ -14,13 +14,10 @@
 namespace skiagm {
 
 static SkBitmap make_bitmap() {
-    SkBitmap bm;
-
-    SkColorTable* ctable = new SkColorTable(1);
-    SkPMColor* c = ctable->lockColors();
-    c[0] = SkPackARGB32(0x80, 0x80, 0, 0);
-    ctable->unlockColors(true);
+    const SkPMColor c[] = { SkPackARGB32(0x80, 0x80, 0, 0) };
+    SkColorTable* ctable = new SkColorTable(c, SK_ARRAY_COUNT(c));
 
+    SkBitmap bm;
     bm.setConfig(SkBitmap::kIndex8_Config, 1, 1);
     bm.allocPixels(ctable);
     ctable->unref();