Update in-tree Google Benchmark to current ToT.

I've put some work into the Google Benchmark library in order to make it easier
to benchmark libc++. These changes have already been upstreamed into
Google Benchmark and this patch applies the changes to the in-tree version.

The main improvement in the addition of a 'compare_bench.py' script which
makes it very easy to compare benchmarks. For example to compare the native
STL to libc++ you would run:

`$ compare_bench.py ./util_smartptr.native.out ./util_smartptr.libcxx.out`

And the output would look like:

RUNNING: ./util_smartptr.native.out
Benchmark                          Time           CPU Iterations
----------------------------------------------------------------
BM_SharedPtrCreateDestroy         62 ns         62 ns   10937500
BM_SharedPtrIncDecRef             31 ns         31 ns   23972603
BM_WeakPtrIncDecRef               28 ns         28 ns   23648649
RUNNING: ./util_smartptr.libcxx.out
Benchmark                          Time           CPU Iterations
----------------------------------------------------------------
BM_SharedPtrCreateDestroy         46 ns         46 ns   14957265
BM_SharedPtrIncDecRef             31 ns         31 ns   22435897
BM_WeakPtrIncDecRef               34 ns         34 ns   21084337
Comparing ./util_smartptr.native.out to ./util_smartptr.libcxx.out
Benchmark                          Time           CPU
-----------------------------------------------------
BM_SharedPtrCreateDestroy         -0.26         -0.26
BM_SharedPtrIncDecRef             +0.00         +0.00
BM_WeakPtrIncDecRef               +0.21         +0.21

llvm-svn: 278147
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: f6e09e537bab92bac0c0f9cfaa4f79761356bf7e
diff --git a/benchmarks/ContainerBenchmarks.hpp b/benchmarks/ContainerBenchmarks.hpp
index 6350e6b..973a135 100644
--- a/benchmarks/ContainerBenchmarks.hpp
+++ b/benchmarks/ContainerBenchmarks.hpp
@@ -10,7 +10,7 @@
 
 template <class Container, class GenInputs>
 void BM_ConstructIterIter(benchmark::State& st, Container, GenInputs gen) {
-    auto in = gen(st.range_x());
+    auto in = gen(st.range(0));
     const auto end = in.end();
     benchmark::DoNotOptimize(&in);
     while (st.KeepRunning()) {
@@ -21,7 +21,7 @@
 
 template <class Container, class GenInputs>
 void BM_InsertValue(benchmark::State& st, Container c, GenInputs gen) {
-    auto in = gen(st.range_x());
+    auto in = gen(st.range(0));
     const auto end = in.end();
     while (st.KeepRunning()) {
         c.clear();
@@ -34,7 +34,7 @@
 
 template <class Container, class GenInputs>
 void BM_InsertValueRehash(benchmark::State& st, Container c, GenInputs gen) {
-    auto in = gen(st.range_x());
+    auto in = gen(st.range(0));
     const auto end = in.end();
     while (st.KeepRunning()) {
         c.clear();
@@ -49,7 +49,7 @@
 
 template <class Container, class GenInputs>
 void BM_InsertDuplicate(benchmark::State& st, Container c, GenInputs gen) {
-    auto in = gen(st.range_x());
+    auto in = gen(st.range(0));
     const auto end = in.end();
     c.insert(in.begin(), in.end());
     benchmark::DoNotOptimize(&c);
@@ -65,7 +65,7 @@
 
 template <class Container, class GenInputs>
 void BM_EmplaceDuplicate(benchmark::State& st, Container c, GenInputs gen) {
-    auto in = gen(st.range_x());
+    auto in = gen(st.range(0));
     const auto end = in.end();
     c.insert(in.begin(), in.end());
     benchmark::DoNotOptimize(&c);
@@ -80,7 +80,7 @@
 
 template <class Container, class GenInputs>
 static void BM_Find(benchmark::State& st, Container c, GenInputs gen) {
-    auto in = gen(st.range_x());
+    auto in = gen(st.range(0));
     c.insert(in.begin(), in.end());
     benchmark::DoNotOptimize(&(*c.begin()));
     const auto end = in.data() + in.size();
@@ -95,7 +95,7 @@
 template <class Container, class GenInputs>
 static void BM_FindRehash(benchmark::State& st, Container c, GenInputs gen) {
     c.rehash(8);
-    auto in = gen(st.range_x());
+    auto in = gen(st.range(0));
     c.insert(in.begin(), in.end());
     benchmark::DoNotOptimize(&(*c.begin()));
     const auto end = in.data() + in.size();