[wasm][cleanup] Minor cleanup of comments and code

R=ahaas@chromium.org

Change-Id: Id21608780e345448398ad4066ad307bef7358801
Reviewed-on: https://chromium-review.googlesource.com/849832Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50396}

src/wasm/function-body-decoder.cc

@@ -731,13 +731,12 @@ class WasmGraphBuildingInterface {
     return loop_body_env;
   }
 
-  // Create a complete copy of the {from}.
+  // Create a complete copy of {from}.
   SsaEnv* Split(Decoder* decoder, SsaEnv* from) {
     DCHECK_NOT_NULL(from);
     SsaEnv* result =
         reinterpret_cast<SsaEnv*>(decoder->zone()->New(sizeof(SsaEnv)));
-    // The '+ 2' here is to accommodate for mem_size and mem_start nodes.
-    size_t size = sizeof(TFNode*) * (decoder->NumLocals());
+    size_t size = sizeof(TFNode*) * decoder->NumLocals();
     result->control = from->control;
     result->effect = from->effect;