[wasm][cleanup] Add constructor for FunctionBody

Also, remove {FunctionBodyForTesting}, which is only being used once.
Use the constructor directly instead.

R=ahaas@chromium.org

Change-Id: Ieceac41bf62ec2accf1bb39d8334563557c0dbbd
Reviewed-on: https://chromium-review.googlesource.com/847514
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50397}

src/wasm/function-body-decoder.cc

@@ -879,7 +879,7 @@ std::pair<uint32_t, uint32_t> StackEffect(const WasmModule* module,
 
 void PrintRawWasmCode(const byte* start, const byte* end) {
   AccountingAllocator allocator;
-  PrintRawWasmCode(&allocator, FunctionBodyForTesting(start, end), nullptr);
+  PrintRawWasmCode(&allocator, FunctionBody{nullptr, 0, start, end}, nullptr);
 }
 
 namespace {

src/wasm/function-body-decoder.h

@@ -34,12 +34,11 @@ struct FunctionBody {
   uint32_t offset;    // offset in the module bytes, for error reporting
   const byte* start;  // start of the function body
   const byte* end;    // end of the function body
-};
 
-static inline FunctionBody FunctionBodyForTesting(const byte* start,
-                                                  const byte* end) {
-  return {nullptr, 0, start, end};
-}
+  FunctionBody(FunctionSig* sig, uint32_t offset, const byte* start,
+               const byte* end)
+      : sig(sig), offset(offset), start(start), end(end) {}
+};
 
 V8_EXPORT_PRIVATE DecodeResult VerifyWasmCode(AccountingAllocator* allocator,
                                               const wasm::WasmModule* module,
@@ -63,14 +62,14 @@ void PrintRawWasmCode(const byte* start, const byte* end);
 inline DecodeResult VerifyWasmCode(AccountingAllocator* allocator,
                                    const WasmModule* module, FunctionSig* sig,
                                    const byte* start, const byte* end) {
-  FunctionBody body = {sig, 0, start, end};
+  FunctionBody body(sig, 0, start, end);
   return VerifyWasmCode(allocator, module, body);
 }
 
 inline DecodeResult BuildTFGraph(AccountingAllocator* allocator,
                                  TFBuilder* builder, FunctionSig* sig,
                                  const byte* start, const byte* end) {
-  FunctionBody body = {sig, 0, start, end};
+  FunctionBody body(sig, 0, start, end);
   return BuildTFGraph(allocator, builder, body);
 }