Bump SkXMLParser buffer size

Current release value is smallish (512) and debug is terribly
inefficient (5).  Bump to 4K for both release/debug builds.

(I think the small debug value was meant to artificially stress Expat
streaming, but it seems unnecessary nowadays).

Change-Id: I459afce5dde9789da84baaa68c4db9164911ffa1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/351200
Reviewed-by: Tyler Denniston <tdenniston@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Florin Malita <fmalita@google.com>
diff --git a/src/xml/SkXMLParser.cpp b/src/xml/SkXMLParser.cpp
index bf47897..fb31e06 100644
--- a/src/xml/SkXMLParser.cpp
+++ b/src/xml/SkXMLParser.cpp
@@ -153,7 +153,7 @@
     // Disable entity processing, to inhibit internal entity expansion. See expat CVE-2013-0340.
     XML_SetEntityDeclHandler(ctx.fXMLParser, entity_decl_handler);
 
-    static const int kBufferSize = 512 SkDEBUGCODE( - 507);
+    static constexpr int kBufferSize = 4096;
     bool done = false;
     do {
         void* buffer = XML_GetBuffer(ctx.fXMLParser, kBufferSize);