Revert "[base] Make USE a variadic template"

This reverts commit 39e335c7.

Reason for revert: Breaks debug builds on Linux, especially mksnapshot fails now, i.e.:

FAILED: mksnapshot
python "../../build/toolchain/gcc_link_wrapper.py" --output="./mksnapshot" -- ../../third_party/llvm-build/Release+Asserts/bin/clang++ -pie -Wl,--fatal-warnings -fPIC -Wl,-z,noexecstack -Wl,-z,now -Wl,-z,relro -Wl,-z,defs -Wl,--no-as-needed -lpthread -Wl,--as-needed -fuse
-ld=gold -B../../third_party/binutils/Linux_x64/Release/bin -Wl,--threads -Wl,--thread-count=4 -Wl,--icf=all -m64 -Werror -Wl,--gdb-index --sysroot=../../build/linux/debian_jessie_amd64-sysroot -L../../build/linux/debian_jessie_amd64-sysroot/lib/x86_64-linux-gnu -Wl,-rpat
h-link=../../build/linux/debian_jessie_amd64-sysroot/lib/x86_64-linux-gnu -L../../build/linux/debian_jessie_amd64-sysroot/usr/lib/x86_64-linux-gnu -Wl,-rpath-link=../../build/linux/debian_jessie_amd64-sysroot/usr/lib/x86_64-linux-gnu -Wl,-rpath-link=. -Wl,--disable-new-dt
ags -rdynamic -nodefaultlibs -o "./mksnapshot" -Wl,--start-group @"./mksnapshot.rsp"  -Wl,--end-group   -ldl -lpthread -lrt -lc -lm -lgcc_s
../../src/elements.cc:3362: error: undefined reference to 'v8::internal::(anonymous namespace)::ElementsKindTraits<(v8::internal::ElementsKind)7>::Kind'
../../src/elements.cc:3362: error: undefined reference to 'v8::internal::(anonymous namespace)::ElementsKindTraits<(v8::internal::ElementsKind)8>::Kind'
../../src/elements.cc:3953: error: undefined reference to 'v8::internal::(anonymous namespace)::ElementsKindTraits<(v8::internal::ElementsKind)9>::Kind'
../../src/profiler/heap-snapshot-generator.cc:187: error: undefined reference to 'v8::internal::(anonymous namespace)::SnapshotSizeConstants<4ul>::kExpectedHeapGraphEdgeSize'
../../src/elements.cc:3953: error: undefined reference to 'v8::internal::(anonymous namespace)::ElementsKindTraits<(v8::internal::ElementsKind)10>::Kind'
../../src/profiler/heap-snapshot-generator.cc:198: error: undefined reference to 'v8::internal::(anonymous namespace)::SnapshotSizeConstants<4ul>::kExpectedHeapEntrySize'
../../src/profiler/heap-snapshot-generator.cc:199: error: undefined reference to 'v8::internal::(anonymous namespace)::SnapshotSizeConstants<8ul>::kExpectedHeapGraphEdgeSize'
../../src/profiler/heap-snapshot-generator.cc:200: error: undefined reference to 'v8::internal::(anonymous namespace)::SnapshotSizeConstants<8ul>::kExpectedHeapEntrySize'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

Original change's description:
> [base] Make USE a variadic template
> 
> This will allow for passing more than one variable. This is
> particularly interesting for calling a method on each type in a
> parameter pack, as in:
> 
> template<typename... T>
> void foo(T&&... ts) {
>   USE(do_something(ts)...);
> }
> 
> Drive-by fix: Allow to pass arbitrary types to USE, including
> references. This might prevent a copy for pass-by-value.
> 
> R=​ishell@chromium.org
> 
> Change-Id: I8f894d730bbcd195ed83705f98771994b4bc906f
> Reviewed-on: https://chromium-review.googlesource.com/565561
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#46527}

TBR=clemensh@chromium.org,ishell@chromium.org

Change-Id: Ibd3f0529e7a3136c4bcac15443da3d9f8dde8510
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/565141Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46534}

src/base/macros.h

@@ -190,8 +190,9 @@ V8_INLINE Dest bit_cast(Source const& source) {
 
 // The USE(x) template is used to silence C++ compiler warnings
 // issued for (yet) unused variables (typically parameters).
-template <typename... Ts>
-inline void USE(Ts&&...) {}
+template <typename T>
+inline void USE(T) { }
+
 
 #define IS_POWER_OF_TWO(x) ((x) != 0 && (((x) & ((x) - 1)) == 0))
 

test/unittests/base/platform/platform-unittest.cc

@@ -154,8 +154,7 @@ class MemoryAllocationPermissionsTest : public ::testing::Test {
     if (!sigsetjmp(continuation_, save_sigs)) {
       switch (action) {
         case MemoryAction::kRead: {
-          // static_cast to remove the reference and force a memory read.
-          USE(static_cast<int>(*buffer));
+          USE(*buffer);
           break;
         }
         case MemoryAction::kWrite: {