alternative no anonymous enums

Anonymous enums play havoc with documentation;
there's no name to refer to. It may be that all
enums may either be named or replaced with constexpr
without breaking anything. Try replacing all
anonymous enums in include/core to see what happens.

This names SkCanvas::SaveLayerFlagsSet but leaves
SkCanvas::SaveLayerFlags as a uint32_t, to reduce
risk as compared to review.skia.org/123584.

There's also some chance that external linkage will
break if some client refers to anonymous enum in a way
that could require its address: see
https://stackoverflow.com/questions/22867654/enum-vs-constexpr-for-actual-static-constants-inside-classes
(This CL does not require definitions + declarations)

Brought bookmaker docs in line with this change.
This also tripped over missing code in bookmaker
handling constexpr so added that as well.

R=reed@google.com,bsalomon@google.com

Docs-Preview: https://skia.org/?cl=123920
Docs-Preview: https://skia.org/?cl=123584
Bug: skia:6898
Change-Id: I14a342edcfd59e139ef9e4501f562417c4c60391
Reviewed-on: https://skia-review.googlesource.com/123920
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Cary Clark <caryclark@skia.org>
diff --git a/docs/SkCanvas_Reference.bmh b/docs/SkCanvas_Reference.bmh
index 0bce15e..f4672c4 100644
--- a/docs/SkCanvas_Reference.bmh
+++ b/docs/SkCanvas_Reference.bmh
@@ -1678,15 +1678,17 @@
 documentation purposes, this enum is named rather than anonymous
 ##
 
-#Enum
+#Enum SaveLayerFlagsSet
 #Line # sets SaveLayerRec options ##
 #Code
-    enum {
+    enum SaveLayerFlagsSet {
         kPreserveLCDText_SaveLayerFlag = 1 << 1,
         kInitWithPrevious_SaveLayerFlag = 1 << 2,
         kMaskAgainstCoverage_EXPERIMENTAL_DONT_USE_SaveLayerFlag = 1 << 3,
         kDontClipToLayer_Legacy_SaveLayerFlag = kDontClipToLayer_PrivateSaveLayerFlag,
     };
+
+    typedef uint32_t SaveLayerFlags;
 ##
 
 SaveLayerFlags provides options that may be used in any combination in SaveLayerRec,
@@ -1838,7 +1840,8 @@
 
 ##
 
-#Method SaveLayerRec(const SkRect* bounds, const SkPaint* paint, SaveLayerFlags saveLayerFlags = 0)
+#Method SaveLayerRec(const SkRect* bounds, const SkPaint* paint,
+        SaveLayerFlags saveLayerFlags = 0)
 
 Sets fBounds, fPaint, and fSaveLayerFlags; sets fBackdrop to nullptr.