Add missing stdint include

In file included from ../../chrome/browser/vr/sample_queue.cc:5:
../../chrome/browser/vr/sample_queue.h:22:3: error: unknown type name 'int64_t'
  int64_t GetSum() const { return sum_; }
  ^
../../chrome/browser/vr/sample_queue.h:24:18: error: unknown type name 'int64_t'
  void AddSample(int64_t value);
                 ^
../../chrome/browser/vr/sample_queue.h:32:3: error: unknown type name 'int64_t'
  int64_t sum_ = 0;
  ^
../../chrome/browser/vr/sample_queue.h:35:15: error: use of undeclared identifier 'int64_t'

  std::vector<int64_t> samples_;
              ^
../../chrome/browser/vr/sample_queue.cc:17:19: error: out-of-line definition of 'AddSample' does not match any declaration in 'vr::SampleQueue'
void SampleQueue::AddSample(int64_t value) {
                  ^~~~~~~~~

[choco@choco-rhel6-vm chromium-65.0.3325.31]$ /opt/rh/llvm-toolset-7/root/usr/bin/clang++ -v
clang version 4.0.1 (tags/RELEASE_401/final)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/rh/llvm-toolset-7/root/usr/bin
Found candidate GCC installation: /opt/rh/devtoolset-6/root/usr/lib/gcc/x86_64-redhat-linux/6.3.1
Found candidate GCC installation: /opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/4.4.7
Selected GCC installation: /opt/rh/devtoolset-7/root/usr/lib/gcc/x86_64-redhat-linux/7
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Icb4db046d907eb0dde94201d8b5bd8082e10337e

TBR=bajones@chromium.org

Change-Id: Icb4db046d907eb0dde94201d8b5bd8082e10337e
Reviewed-on: https://chromium-review.googlesource.com/895583Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533343}

chrome/browser/vr/sample_queue.cc

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <stdint.h>
+
 #include "chrome/browser/vr/sample_queue.h"
 
 namespace vr {