[wasm] Fix MSVC compile error

MSVC wants the static cast, even if the constant fits in the narrower
type anyway.

R=ahaas@chromium.org

Change-Id: I40043c02db1524ac591f6dcea14333695a53d028
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1924356Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65482}

src/wasm/value-type.h

@@ -108,8 +108,10 @@ class LoadType {
   const LoadTypeValue val_;
 
   static constexpr uint8_t kLoadSizeLog2[] = {
+  // MSVC wants a static_cast here.
 #define LOAD_SIZE(_, __, memtype) \
-  ElementSizeLog2Of(MachineType::memtype().representation()),
+  static_cast<uint8_t>(           \
+      ElementSizeLog2Of(MachineType::memtype().representation())),
       FOREACH_LOAD_TYPE(LOAD_SIZE)
 #undef LOAD_SIZE
   };
@@ -176,8 +178,9 @@ class StoreType {
   const StoreTypeValue val_;
 
   static constexpr uint8_t kStoreSizeLog2[] = {
+  // MSVC wants a static_cast here.
 #define STORE_SIZE(_, __, memrep) \
-  ElementSizeLog2Of(MachineRepresentation::k##memrep),
+  static_cast<uint8_t>(ElementSizeLog2Of(MachineRepresentation::k##memrep)),
       FOREACH_STORE_TYPE(STORE_SIZE)
 #undef STORE_SIZE
   };