[wasm] Remove global HandleScope in streaming compilation tests

The streaming compilation cctests test streaming compilation over the
public API, as far as possible. It is not required that a HandleScope
is open when the API is used. Therefore the cctest should also not open
a global HandleScope for a whole test but as fine-grained as possible.

R=clemensh@chromium.org

Bug: v8:8055 v8:8015
Change-Id: Id5e2145f2a8ba66e8d5d9021c47806aa80fc463f
Reviewed-on: https://chromium-review.googlesource.com/1174258Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55113}

test/cctest/wasm/test-streaming-compilation.cc

@@ -109,6 +109,7 @@ class StreamTester {
   StreamTester() : zone_(&allocator_, "StreamTester") {
     v8::Isolate* isolate = CcTest::isolate();
     i::Isolate* i_isolate = CcTest::i_isolate();
+    i::HandleScope internal_scope(i_isolate);
 
     v8::Local<v8::Context> context = isolate->GetCurrentContext();
 
@@ -151,8 +152,6 @@ class StreamTester {
   TEST(name) {                                          \
     MockPlatform platform;                              \
     CcTest::InitializeVM();                             \
-    v8::HandleScope handle_scope(CcTest::isolate());    \
-    i::HandleScope internal_scope(CcTest::i_isolate()); \
     RunStream_##name();                                 \
   }                                                     \
   void RunStream_##name()