Fix a few spelling errors in comments.

ppapi/tests/test_instance_deprecated.cc

Index: ppapi/tests/test_instance_deprecated.cc
diff --git a/ppapi/tests/test_instance_deprecated.cc b/ppapi/tests/test_instance_deprecated.cc
index e4235b84878451e95550095de6a51e73fd6383cb..0aef5ab87668c579be56d8bd6f3f65bd2d41d17d 100644
--- a/ppapi/tests/test_instance_deprecated.cc
+++ b/ppapi/tests/test_instance_deprecated.cc
@@ -74,7 +74,7 @@ bool TestInstance::Init() {
 TestInstance::~TestInstance() {
   ResetTestObject();
   if (testing_interface_->IsOutOfProcess() == PP_FALSE) {
-    // This should cause the instance object's descructor to be called.
+    // This should cause the instance object's destructor to be called.
     testing_interface_->RunV8GC(instance_->pp_instance());
 
     // Test a post-condition which ensures the instance objects destructor is