Revert "Partial revert of "Remove ~MaybeHandle and statically assert that...

Revert "Partial revert of "Remove ~MaybeHandle and statically assert that handles are trivially copyable""

This reverts commit 1dfaec26.

Reason for revert: Does not fix the performance regression, see bug.

Original change's description:
> Partial revert of "Remove ~MaybeHandle and statically assert that handles are trivially copyable"
> 
> Reason: cause Blink regression on Android
> 
> Original CL: https://chromium-review.googlesource.com/c/538463/
> 
> Bug: chromium:735910
> Change-Id: I405e71f6ffeaf9fa467036a6fafa0271a60de9d3
> Reviewed-on: https://chromium-review.googlesource.com/593247
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Commit-Queue: Loo Rong Jie <loorongjie@gmail.com>
> Cr-Commit-Position: refs/heads/master@{#46995}

R=yangguo@chromium.org,loorongjie@gmail.com,jbroman@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:735910
Change-Id: I65eecd575fb1b77471c6dd83a01df6c4e8a85214
Reviewed-on: https://chromium-review.googlesource.com/603797Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47213}

src/base/macros.h

@@ -189,6 +189,13 @@ V8_INLINE Dest bit_cast(Source const& source) {
 // TODO(all) Replace all uses of this macro with static_assert, remove macro.
 #define STATIC_ASSERT(test) static_assert(test, #test)
 
+// TODO(rongjie) Remove this workaround once we require gcc >= 5.0
+#if __GNUG__ && __GNUC__ < 5
+#define IS_TRIVIALLY_COPYABLE(T) \
+  (__has_trivial_copy(T) && __has_trivial_destructor(T))
+#else
+#define IS_TRIVIALLY_COPYABLE(T) std::is_trivially_copyable<T>::value
+#endif
 
 // The USE(x, ...) template is used to silence C++ compiler warnings
 // issued for (yet) unused variables (typically parameters).

src/handles.cc

@@ -12,6 +12,15 @@
 namespace v8 {
 namespace internal {
 
+// Handles should be trivially copyable so that they can be efficiently passed
+// by value. If they are not trivially copyable, they cannot be passed in
+// registers.
+static_assert(IS_TRIVIALLY_COPYABLE(HandleBase),
+              "HandleBase should be trivially copyable");
+static_assert(IS_TRIVIALLY_COPYABLE(Handle<Object>),
+              "Handle<Object> should be trivially copyable");
+static_assert(IS_TRIVIALLY_COPYABLE(MaybeHandle<Object>),
+              "MaybeHandle<Object> should be trivially copyable");
 
 #ifdef DEBUG
 bool HandleBase::IsDereferenceAllowed(DereferenceCheckMode mode) const {

src/handles.h

@@ -185,7 +185,6 @@ template <typename T>
 class MaybeHandle final {
  public:
   V8_INLINE MaybeHandle() {}
-  V8_INLINE ~MaybeHandle() {}
 
   // Constructor for handling automatic up casting from Handle.
   // Ex. Handle<JSArray> can be passed when MaybeHandle<Object> is expected.