Implement querying CPU time on Windows for systemInfo.cpu API

chrome/browser/extensions/api/system_info_cpu/cpu_info_provider_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/system_info_cpu/cpu_info_provider.h"
 
+#include <windows.h>
+#include <winternl.h>
+
+#include "base/sys_info.h"
+
 namespace extensions {
 
+namespace {
+
+const wchar_t kNtdll[] = L"ntdll.dll";
+const char kNtQuerySystemInformationName[] = "NtQuerySystemInformation";
+
+// See MSDN about NtQuerySystemInformation definition.
+typedef DWORD (WINAPI *NtQuerySystemInformationPF)(DWORD system_info_class,
+                                                   PVOID system_info,
+                                                   ULONG system_info_length,
+                                                   PULONG return_length);
+
+}  // namespace
+
 bool CpuInfoProvider::QueryCpuTimePerProcessor(std::vector<CpuTime>* times) {
-  // TODO(hongbo): use NtQuerySystemInformation to query the cpu time.
-  return false;
+  std::vector<CpuTime> results;
+
+  HMODULE ntdll = GetModuleHandle(kNtdll);
+  CHECK(ntdll != NULL);
+  NtQuerySystemInformationPF NtQuerySystemInformation =
+      reinterpret_cast<NtQuerySystemInformationPF>(
+          ::GetProcAddress(ntdll, kNtQuerySystemInformationName));
+
+  CHECK(NtQuerySystemInformation != NULL);
+
+  int num_of_processors = base::SysInfo::NumberOfProcessors();
+  scoped_array<SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION> processor_info(
+      new SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION[num_of_processors]);
+
+  ULONG returned_bytes = 0, bytes =
+      sizeof(SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION) * num_of_processors;
+  if (!NT_SUCCESS(NtQuerySystemInformation(
+          SystemProcessorPerformanceInformation,
+          processor_info.get(), bytes, &returned_bytes)))
+    return false;
+
+  int returned_num_of_processors =
+      returned_bytes / sizeof(SYSTEM_PROCESSOR_PERFORMANCE_INFORMATION);
+
+  if (returned_num_of_processors != num_of_processors)
+    return false;
+
+  results.reserve(returned_num_of_processors);
+  for (int i = 0; i < returned_num_of_processors; ++i) {
+    CpuTime time;
+    time.kernel = processor_info[i].KernelTime.QuadPart;
+    time.user = processor_info[i].UserTime.QuadPart;
+    time.idle = processor_info[i].IdleTime.QuadPart;
+    results.push_back(time);
+  }
+
+  times->swap(results);
+  return true;
 }
 
 }  // namespace extensions