Fix some leaks and failures under valgrind in JS extensions unit tests.

extensions/renderer/module_system_test.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/renderer/module_system_test.h"
 
 #include <map>
 #include <string>
 
 #include "base/callback.h"
@@ skipping 191 matching lines @@
     const std::string& name) {
   v8::EscapableHandleScope handle_scope(isolate_);
   v8::Local<v8::Object> object = v8::Object::New(isolate_);
   isolate_->GetCurrentContext()->Global()->Set(
       v8::String::NewFromUtf8(isolate_, name.c_str()), object);
   return handle_scope.Escape(object);
 }
 
 ModuleSystemTest::ModuleSystemTest()
     : isolate_(v8::Isolate::GetCurrent()),
-      env_(CreateEnvironment()),
       should_assertions_be_made_(true) {
 }
 
 ModuleSystemTest::~ModuleSystemTest() {
 }
 
+void ModuleSystemTest::SetUp() {
+  env_ = CreateEnvironment();
+}
+
 void ModuleSystemTest::TearDown() {
   // All tests must assert at least once unless otherwise specified.
   EXPECT_EQ(should_assertions_be_made_,
             env_->assert_natives()->assertion_made());
   EXPECT_FALSE(env_->assert_natives()->failed());
+  env_.reset();
+  v8::HeapStatistics stats;
+  isolate_->GetHeapStatistics(&stats);
+  size_t old_heap_size = 0;
+  // Run the GC until the heap size reaches a steady state to ensure that
+  // all the garbage is collected.
+  while (stats.used_heap_size() != old_heap_size) {
+    old_heap_size = stats.used_heap_size();
+    isolate_->RequestGarbageCollectionForTesting(
+        v8::Isolate::kFullGarbageCollection);
+    isolate_->GetHeapStatistics(&stats);
+  }
 }
 
 scoped_ptr<ModuleSystemTestEnvironment> ModuleSystemTest::CreateEnvironment() {
   return make_scoped_ptr(new ModuleSystemTestEnvironment(isolate_));
 }
 
 void ModuleSystemTest::ExpectNoAssertionsMade() {
   should_assertions_be_made_ = false;
 }
 
 void ModuleSystemTest::RunResolvedPromises() {
   isolate_->RunMicrotasks();
 }
 
 }  // namespace extensions