Add narrowing casts for VC++ compatibility

New versions of C++ make aggregate initalization with truncation a hard
error. VC++ gives warnings if old initialization syntaxes are used, for
backwards compatibility, but gives a hard error for C++ 11 syntax.

This change adds the casts needed to make this one spot build, which is
sufficient since it is currently the only troublesome spot by the VC++
rules.

Change-Id: I3b597cc8ce628135cfdbb3b91a8b2f9d54562d34
Reviewed-on: https://chromium-review.googlesource.com/1039195
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555683}

components/zucchini/image_utils.h

@@ -183,7 +183,9 @@ constexpr ExecutableType CastToExecutableType(uint32_t possible_exe_type) {
 
 inline std::string CastExecutableTypeToString(ExecutableType exe_type) {
   uint32_t v = static_cast<uint32_t>(exe_type);
-  return {v & 0xFF, (v >> 8) & 0xFF, (v >> 16) & 0xFF, (v >> 24) & 0xFF};
+  char result[] = {v & 0xFF, (v >> 8) & 0xFF, (v >> 16) & 0xFF,
+                   (v >> 24) & 0xFF, 0};
+  return result;
 }
 
 // A region in an image with associated executable type |exe_type|. If