[wasm] [decoder] Also trace global index

With --trace-wasm-decoder, we were printing the local variable index
for values on the stack generated by get_local instructions. This CL
adds the same feature for globals.

R=titzer@chromium.org

Change-Id: Ie113ebcc2d1abcd67df2d01bf4bdb452635732c8
Reviewed-on: https://chromium-review.googlesource.com/684737Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48170}

src/wasm/function-body-decoder-impl.h

@@ -1751,14 +1751,16 @@ class WasmFullDecoder : public WasmDecoder<validate> {
               PrintF("[%d]", operand.value);
               break;
             }
-            case kExprGetLocal: {
+            case kExprGetLocal:
+            case kExprSetLocal:
+            case kExprTeeLocal: {
               LocalIndexOperand<validate> operand(this, val.pc);
               PrintF("[%u]", operand.index);
               break;
             }
-            case kExprSetLocal:  // fallthru
-            case kExprTeeLocal: {
-              LocalIndexOperand<validate> operand(this, val.pc);
+            case kExprGetGlobal:
+            case kExprSetGlobal: {
+              GlobalIndexOperand<validate> operand(this, val.pc);
               PrintF("[%u]", operand.index);
               break;
             }